# Descartes Cogito Argument Essay Ideas

The Final Examination will consist of four half-hour essays, two on Descartes and two on Hume, on essay topics that will be distributed in advance.  In non- writing sections, the course grade will be the better of the quiz-and-recitation grade and the Final Examination grade.  In writing sections, papers and revisions will count for 25% of the course grade; the other 75% of the course grade will be based on the better of the quiz-and-recitation grade and the Final Examination grade.

{Two topics from Group A and one topic from Group B will be omitted from the actual final examination.  Otherwise, the final examination will be exactly like this preview.}

GROUP A (DESCARTES):
D1.  Descartes's 4-Part Method
In the epiphany he experienced in the stove-heated tent on November 10, , Descartes somehow espied the 4-part method whereby he claimed to have later made remarkable discoveries.  In what does this method consist?  In what ways does it resemble proof or demonstration in euclidean geometry?  Are its rules algorithmic (like the rules of long division), i.e., is creativity unnecessary when applying them?  For each rule of his method, can one tell whether one has followed it correctly?  What are the starting points of the method?  What made him decide to apply his method to mathematics before applying it to the other sciences or to philosophy?  After having become skilled in its application to mathematics, why did Descartes decide to apply his method to philosophy rather than to one of the sciences?

D2.  Descartes's Provisional Moral Code
Why does Descartes find it necessary to formulate and adopt a provisional moral code?  In what does it consist?  Is it a radical or conservative code?  Is it provincial?  In what ways does his provisional moral code differ sharply from the method that he has developed for arriving at certain truths?  What is "Stoic" about his provisional moral code?  How does he use the old Scholastic principle that "the will naturally tends to desire only what the intellect represents to it as somehow possible" to  justify his second provisional moral maxim?  What occupation does Descartes adopt?  Does he think it to be the best occupation?  Why?

D3.  Descartes's Language and Action Tests
Explain carefully Descartes's so-called Language Test for discriminating between humans and robots.  What, according to Descartes, makes this test work infallibly?  What kind of certainty does it produce?  Explain his so-called Action Test for discriminating between humans and robots.  Is it an infallible test?  What kind of certainty does it generate?   Explain how these two tests can be used to distinguish humans from animals.  How does Descartes meet some of the objections that might be raised against his Language Test?  How does he appeal to animal failure to justify his Action Test?

D4.  Descartes on Observation and Experimentation
Why does Descartes think that observations become more important the further one goes in knowledge?  At the outset of inquiry into nature, should one rest content with natural (spontaneous) observations or should one seek more recondite observations via deliberate, contrived experiments?  Why?  What order does Descartes follow with respect to observations?  What problems does he encounter at the third stage, i.e., after first having dealt with God and the first principles or causes of everything that exists, and secondly with the first and most ordinary effects deducible from these causes?  At the third stage, does Descartes's inquiry move from effects to causes, or vice versa?  What holds him back from further progress?  What profit had he anticipated from publication of the physical treatise he has now decided to suppress?

D5.  Descartes's Method of Doubt in the First Meditation
Why is Descartes so obsessed with doubt?  Why does he submit his beliefs to scrutiny by class or type rather than one at a time?  What causes him to doubt his sense-based beliefs?  To doubt beliefs such as that he has a head and hands?  To doubt his mathematical beliefs?  What is the Evil Demon hypothesis?  What function does it serve?  Is there any way for Descartes to frustrate the Evil Demon?  Formulate Descartes's dream hypothesis.  Why does he advance it?  Which of his beliefs does it call into doubt?  Which ones does it leave intact?  Is he able to reject the dream hypothesis in this Meditation?

D6.  "Cogito ergo sum"  ("je pense donc je suis") in the Second Meditation
What is the Cogito, a proposition or an argument or a bit of both?  How does Descartes derive it?  What does he mean by thinking?  How certain is Descartes that he is thinking?  On what grounds?  How certain is he that he exists?  On what grounds?  How certain or indubitable is the Cogito itself?  What does the Cogito tell Descartes about his own nature?

D7.  Descartes's nature as a thinking thing in the Second Meditation
Why does Descartes reject the traditional answer "rational animal" to the question what his nature is, i.e., what kind of thing he is?   What is his own answer to this question?  Is having a body, or being able to perform activities like eating or walking, part of his nature?  Why or why not?  What does he mean by thinking?  Does he distinguish seeing a horse from seeming to see the horse?  Why or why not?  Is it possible that a body can think?  Is it possible that Descartes is really a body?  Which is more easily and better known: a piece of wax or one's own mind?  Why?

D8.  The Third Meditation Argument for the Existence of God
What at the beginning of this Meditation does Descartes know with certainty to exist?  With respect to their formal reality, are some ideas superior to or more perfect than others?  With respect to their objective reality?  What causal principle does Descartes invoke to escape from solipsism?  How does it apply to ideas?  What kind of idea will enable him to escape solipsism?  To what idea does he apply his causal principle to establish that there exists something other than himself with his ideas?  How does his argument to the existence of God go?  Would this argument still go through if he had applied the causal principle to his idea of himself or to his idea of an angel (a purely spiritual but finite substance)?  Is his idea of an infinite substance a negative or a positive idea?  Why does it matter?  Could his idea of God be materially false?  Why does it matter?

D9.  Error, intellect, and will in the Fourth Meditation
Would God be a malicious deceiver if He placed in me a cognitive faculty that makes mistakes or errors when I use it properly?  Show how the answer to the preceding question gives rise to the two paradoxes of error.  Formulate Descartes's account of error.  Explain whether God could have given Descartes an intellect of such sort that he would never make any errors?  In what sense is Descartes's will equal to God's?  In what sense is it inferior to God's?  Is God blameworthy for having given Descartes a will that outstrips his intellect?  What can Descartes himself do to escape error?  How does he know that this escape from error really works?  If he nonetheless falls into error, does it reflect badly on God?}

D  Descartes's ontological argument in the Fifth Meditation
Where does Descartes get the idea for his ontological argument?  What is it about his idea of a triangle that makes it possible for him to prove that the sum of its interior angles equals degrees?  How does the idea of a unicorn differ from the idea of a triangle?  How cogent are mathematical demonstrations (proofs)?  Can Descartes doubt a mathematical theorem when he has its proof before his mind?  Formulate his ontological proof of the existence of God.  How cogent is it?  Why then does Descartes hesitate to accept its conclusion as an indubitable and certain truth?  Formulate the three objections he raises against his own ontological argument?  How does he answer these objections?  Does he now give his full assent to his ontological argument and its conclusion?}

D  Descartes's Sixth Meditation argument to an external world
What causal principle and what conceptual premiss does Descartes invoke to prove that bodies can exist?  Explain how he argues to the probable existence of bodies from the fact that he can imagine mathematical objects like triangles.  On the basis of what causal principle does Descartes think that his sense ideas (sensations and sense perceptions) must come from one of four sources: himself, bodies, God, or some being intermediate in perfection between bodies and God?  How does Descartes rule out himself as the source of his sense ideas?  Why would God be a malicious deceiver if the source of Descartes's sense ideas was either God Himself or some being intermediate between bodies and God?  What permits Descartes now to conclude that he really does have a body and that material bodies are the sources of his adventitious sense ideas?

D Good-tasting poison, dropsical thirst, and God's veracity in the Sixth Meditation
Distinguish accidental from systematic or intrinsic error?  Is the fact that someone desires to eat a good-tasting but poisoned soup an example of accidental or systematic error?  Does it convict God of malicious deception?  Why or why not?  Is the illness-induced thirst of someone who suffers from dropsy an accidental or a systematic error?  If systematic, does it convict God of malicious deception?  Why or why not?

GROUP B (HUME):
H1.  Simple Idea as Copies of Impressions
What does Hume mean by a perception of the mind?  Into what classes does he divide them?  On what basis?  Is this bipartite classification mutually exclusive?  Jointly exhaustive?  What is an impression?  A simple idea?  A complex idea?  Give examples.  What is inner sense?  Outer sense?  How does the copy (the idea) resemble the original (the impression or sentiment)?  How do they differ?  What are Hume's evidence and arguments for the thesis that simple ideas are copies of impressions?  Does he intend this thesis to be exceptionless, i.e., general or universal?  How then might opponents challenge the thesis?  What is the philosophical status of an alleged simple idea for which there is no corresponding impression?  What is Hume's Microscope and how does this thesis give rise to it?  What is the relevance of the case of the missing shade of blue?  What is Hume's final disposition of this case?

H2.  Hume's Fork
Formulate Hume's Fork.  Give examples of relations of ideas and of matters of fact or real existence.  What is the basis of Hume's Fork?  Does it divide propositions into mutually exclusive and jointly exhaustive classes?  Which propositions are discoverable a priori?  Which are discoverable a posteriori?  Which contradictories are conceivable?  Which propositions take us beyond the immediate deliverances of sense and of memory?  When do people think they have insight into causal relationships?  When do they recognize that they lack such insight?  What allegedly follows from the observation that cause and effect are distinct events?  What is the thought experiment about Adam supposed to show?  To what is human reason limited in causal matters?

H3.  No Rational Justification of Causal Reasoning
What is the nature of all reasoning concerning matters of fact and real existence?  What is the foundation of all our reasonings and conclusions concerning cause-and-effect?  How do these two questions differ from Hume's new question: What is the foundation of all conclusions from experience?  Formulate Hume's negative answer to this new question.  What can past experience tell us about which objects follow upon which objects?  On what basis do we extrapolate from past experience to the future and to unobserved cases?  Is the link between past and future intuitive?  Demonstrative?  Do we appeal to a principle of the uniformity of nature in making such extrapolations?  Can we justify this appeal in a noncircular fashion?  Why don't these considerations show only that Hume isn't clever enough to find a justification for the aforesaid extrapolation?

H4.  Hume's Microscope
Given Hume's theory of ideas as copies of impressions, what is the obvious way or method to eliminate the obscurity and ambiguity of ideas in the moral sciences?  What does Hume take definition to be?  Why does definition serve to clarify and disambiguate only complex ideas?  How, then, does one clarify and disambiguate simple ideas that are obscure or ambiguous?  To what is Hume referring when he speaks of a new microscope or species of optics, by which, in the moral sciences, the most minute, and most simple ideas may be so enlarged as to fall readily under our apprehension?   To which idea, as a test case of philosophical analysis, does Hume apply his new microscope?  Why did he choose to investigate this particular idea?  Why does he look for the impression of which this idea is supposedly a copy, rather than define it by enumerating its component simple ideas?

H5.  Necessary Connection
Does Hume think that the idea of necessary connection is a copy of an impression produced by single instances of physical objects or events that stand in a causal relation?  Why not?  Does it arise from reflection on the operations of the mind?  In particular, does it arise from the control of, or influence over, the body by the will?  What makes Hume think that we come to know the influence of the will over the body only through experience?  Does the idea of necessary connection arise, then, from an impression produced or felt when the mind or will operates on ideas or other mental contents, as when we will to call up ideas or propositions?  What makes Hume think that we learn the influence of will over thoughts and other mental contents only from experience?  What impression does Hume finally identify as the original sentiment of which the idea of necessary connection is a copy?  Is necessary connection, then, a matter of projecting something mental onto the world?  By finding an impression corresponding to the idea, has Hume shown that necessary connection is a philosophically legitimate idea?

H6.  Hume's Touchstone
Does it enhance the credentials of a theory about the human mind when one finds that it is needed to explain operations of animal minds?  What is Hume's Touchstone?  Why does he proceed to apply this touchstone to his theory of experimental reasoning (his theory of how we reason about matters of fact and real existence)?  Does he think that animals, like men, learn many things from experience?  Do they expect that like effects will follow like causes?  Are these inferences or expectations based on past experience?  To what evidence for these claims does Hume point?  Can one account for these animal inferences or expectations as instances of reasoning or argument that invokes some sort of  uniformity of nature principle?  Do human children make causal inferences in this way?  Why not?  Is animal belief to be explained in the same way Hume explained human belief?  Why didn't Nature entrust such important operations as causal inferences to reasoning and argumentation rather than to habit or custom?

H7.  A Priori Knowledge of Matters of Fact
Do animals acquire all their knowledge of matters of fact and real existence from sense perception and causal reasoning?  If not, what is this knowledge like and where do they get it?  What is INSTINCT?  Is causal reasoning itself an instinct?  Do animals have a priori knowledge of matters of fact and real existence?  If so, how can this be reconciled with Hume's system?  Do humans have a priori knowledge of matters of fact and real existence?  If so, where and how do they get it?  If not, are animals cognitively better endowed than humans?

H8.  The Nature of Belief
What does Hume take belief in a proposition to be?  Does he offer a definition of belief?  Why not?  How does he describe the feeling or sentiment of belief?  Would someone who was incapable of feeling have any beliefs?  Which principle of association of ideas is closely tied to belief?  In what way is it tied?  Do resemblance and contiguity by themselves ever give rise to belief?  Why not?

H9. Reliability of Human Testimony and Miracles
How common, useful, and necessary is reasoning based on human testimony?  On what does such reasoning depend?  On past experience of human veracity and of the conformity of events to reports about them?  On the relation of cause and effect?  When does the evidence of human testimony have the status of probability?  When does it become proof?  What factors will enhance the force of testimony?  What factors will diminish it?  Is the improbability of the reported event one of these diminishing factors?  What does Hume mean by a miracle?  If the reported event is miraculous, is this circumstance direct and full proof against its occurrence?  What if the testimony to the miracle is so solid that its falsity would be miraculous, or even more miraculous than the wondrous event?  What should a rational person conclude if he or she finds a miracle supported by absolutely incontrovertible testimony?  Is there ever such testimony for religious miracles?  Why or why not?

The third quiz will count for 30% of the quiz-and-recitation grade (the first quiz and recitation section participation will each count for 20%, the second quiz for 30%).  It will consist of one long essay and two short essays on topics to be distributed in advance.

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ESSAY TOPICS FOR 3RD QUIZ

Long Essay Topics:

L1.  Simple Idea as Copies of Impressions
What does Hume mean by a perception of the mind?  Into what classes does he divide them?  On what basis?  Is this bipartite classification mutually exclusive?  Jointly exhaustive?  What is an impression?  A simple idea?  A complex idea?  Give examples.  What is inner sense?  Outer sense?  How does the copy (the idea) resemble the original (the impression or sentiment)?  How do they differ?  What are Hume's evidence and arguments for the thesis that simple ideas are copies of impressions?  Does he intend this thesis to be exceptionless, i.e., general or universal?  How then might opponents challenge
the thesis?  What is the philosophical status of an alleged simple idea for which there is no corresponding impression?  What is Hume's Microscope and how does this thesis give rise to it?  What is the relevance of the case of the missing  shade of blue?  What is Hume's final disposition of this case?

L2.  Hume's Fork
Formulate Hume's Fork.  Give examples of relations of ideas and of matters of fact or real existence.  What is the basis of Hume's Fork?  Does it divide propositions into mutually exclusive and jointly exhaustive classes? Which propositions are discoverable a priori?  Which are discoverable a posteriori?  Which contradictories are conceivable?  Which propositions take
us beyond the immediate deliverances of sense and of memory?  When do people think they have insight into causal  relationships?  When do they recognize that they lack such insight?  What allegedly follows from the observation that cause
and effect are distinct events?  What is the thought experiment about Adam supposed to show?  To what is human reason limited in causal matters?

L3.  No Rational Justification of Causal Reasoning
What is the nature of all reasoning concerning matters of fact and real existence?  What is the foundation of all our  reasonings and conclusions concerning cause-and-effect?  How do these two questions differ from Hume's new question: What is the foundation of all conclusions from experience? Formulate Hume's negative answer to this new question.  What can past
experience tell us about which objects follow upon which objects?  On what basis do we extrapolate from past experience to the future and to unobserved cases?  Is the link between past and future intuitive?  Demonstrative?  Do we appeal to a principle of the uniformity of nature in making such extrapolations? Can we justify this appeal in a noncircular fashion?  Why don't these
considerations show only that Hume isn't clever enough to find a justification for the aforesaid extrapolation?

L4.  Single versus Multiple Cases
Can single cases of the conjunction of two objects or events ever give rise to the idea of cause-and-effect?  Explain.  How does a multiplicity of cases give rise to this idea?  What does this show about the role of reason or the understanding in generating the idea of cause-and-effect?  Could the understanding by itself ever get beyond what is immediately present to the
senses or to memory?  If reason does not prompt us to draw conclusions from experience, i.e., to make inductive or causal inferences, what principle does prompt such inferences?   What is custom?  Is it a type of instinct?   How does the invocation of custom (habit) remove the difficulty about multiple-case versus single-case causal inferences?  Without custom, what would the range of human knowledge be?  Can we, by reasoning about it, resist custom (habit) when it prompts us to infer one thing from another thing that is present to our senses or memory when we have found the two things constantly conjoined in our  experience?  Is it custom or will, then, that determines what we believe about matters of fact?  Was Descartes wrong to think that we have it always within our power to suspend judgment on any proposition that we do not clearly and distinctly perceive to be true?

L5.  Hume's Microscope
Given Hume's theory of ideas as copies of impressions, what is the obvious way or method to eliminate the obscurity and ambiguity of ideas in the moral sciences?  What does Hume take definition to be?  Why does definition serve to clarify and disambiguate only complex ideas?  How, then, does one clarify and disambiguate simple ideas that are obscure or ambiguous?  To what is Hume referring when he speaks of a new microscope or species of optics, by which, in the moral sciences, the most minute, and most simple ideas may be so enlarged as to fall readily under our apprehension?   To which idea, as a test
case of philosophical analysis, does Hume apply his new microscope?  Why did he choose to investigate this particular idea?  Why does he look for the impression of which this idea is supposedly a copy, rather than define it by enumerating its component simple ideas?

L6.  Necessary Connection
Does Hume think that the idea of necessary connection is a copy of an impression produced by single instances of physical objects or events that stand in a causal relation?  Why not?  Does it arise from reflection on the operations of the mind?  In particular, does it arise from the control of, or influence over, the body by the will?  What makes Hume think that we come to know the influence of the will over the body only through experience?  Does the idea of necessary connection arise, then, from an impression produced or felt when the mind or will operates on ideas or other mental contents, as when we will to call up ideas or propositions?  What makes Hume think that we learn the influence of will over thoughts and other mental contents only from experience?  What impression does Hume finally identify as the original sentiment of which the idea of necessary  connection is a copy?  Is necessary connection, then, a matter of projecting something mental onto the world?  By finding an impression corresponding to the idea, has Hume shown that necessary connection is a philosophically legitimate idea?

L7.  Hume's Touchstone
Does it enhance the credentials of a theory about the human mind when one finds that it is needed to explain operations of animal minds?  What is Hume's Touchstone?  Why does he proceed to apply this touchstone to his theory of experimental reasoning (his theory of how we reason about matters of fact and real existence)?  Does he think that animals, like men, learn many things from experience?  Do they expect that like effects will follow like causes?  Are these inferences or expectations based on past experience?  To what evidence for these claims does Hume point?  Can one account for these animal inferences or expectations as instances of reasoning or argument that invokes some sort of  uniformity of nature principle?  Do human
children make causal inferences in this way?  Why not?  Is animal belief to be explained in the same way Hume explained human belief?  Why didn't Nature entrust such important operations as causal inferences to reasoning and argumentation  rather
than to habit or custom?

L8.  A Priori Knowledge of Matters of Fact
Do animals acquire all their knowledge of matters of fact and real existence from sense perception and causal reasoning?  If not, what is this knowledge like and where do they get it?  What is INSTINCT?  Is causal reasoning itself an instinct?  Do animals have a priori knowledge of matters of fact and real existence?  If so, how can this be reconciled with Hume's system? Do humans have a priori knowledge of matters of fact and real existence?  If so, where and how do they get it?  If not, are animals cognitively better endowed than humans?

S1.  Mental Geography
Why does Hume attach considerable importance to taxonomy in the study of mind when he fully realizes that taxonomy has little value in the natural sciences?  What does he mean by the moral sciences?  Does he expect them to advance beyond the taxonomic stage?  How does he envision progress in these sciences?  Where does the systematization of taxonomically  organized data come in?  Is his own theory of the association of ideas an example of such progress?

S2.  The Missing Shade of Blue
Formulate this thought experiment.  What does Hume think it shows?  Is it a counterexample to his thesis that simple ideas are copies of impressions of sense?  How might Hume have dismissed this thought experiment as unprobative?  Why didn't he do this?  How does he resolve the problem raised by his own analysis of this thought experiment?

S3.  The Association of Ideas
What governs the flow of ideas in our minds?  Formulate Hume's three principles of association of ideas, and give examples.  Does Hume believe these three principles are complete?  In what sense?  On what grounds?  Why is the principle of Cause & Effect so important?  How does it differ from the other two principles?  How is it related to belief?

S4.  Does Scepticism Paralyze?
Why do religion and some types of philosophy corrupt morals, detract from the enjoyment of life, and make one lazy and presumptuous?  Does Hume's brand of scepticism do these things?  Why or why not?  Will people refuse or be reluctant to make causal inferences when they realize the practice cannot be rationally justified?  Why or why not?  Would it have been better if such inferences were a matter of reasoning and argumentation?  Why or why not?

S5.  The Nature of Belief
What does Hume take belief in a proposition to be?  Does he offer a definition of belief?  Why not?  How does he describe the feeling or sentiment of belief?  Would someone who was incapable of feeling have any beliefs?  Which principle of association of ideas is closely tied to belief?  In what way is it tied? Do resemblance and contiguity by themselves ever give rise to belief?  Why not?

S6.  Pre-established Harmony between the Courses of Nature and Ideas
Why does Hume speak of a certain pre-established harmony between the course of Nature and the course of our ideas?  In what does it consist?  Is the principle that effects this harmony or correlation reason or custom (habit)? Explain.  Why is it advantageous to the human organism that it be custom rather than reason that establishes this correspondence?

S7.  Definitions of Cause
Hume advances two definitions of cause, namely, (a) an object, followed by another, and where all the objects similar to the first are followed by objects similar to the second, and (b) an object followed by another, and whose appearance always conveys the thought to that other.  Are these two definitions equivalent?  To which experience does each definition orrespond?  Is the following restatement by Hume of definition (a) really equivalent to definition (a), namely: an object followed by another where, if the first object had not been, the second never had existed?  If not, what are we to make of this restatement of  definition (a)?

S8.  Reliability of Human Testimony
How common, useful, and necessary is reasoning based on human testimony?  On what does such reasoning depend?  On past experience of human veracity and of the conformity of events to reports about them?  On the relation of cause and effect?  When does the evidence of human testimony have the status of probability?  When does it become proof?  What factors will enhance the force of testimony?  What factors will diminish it?  Is the improbability of the reported event one of these  diminishing factors?

S9.  Miracles
What does Hume mean by a miracle?  If the reported event is miraculous, is this circumstance direct and full proof against its occurrence?  What if the testimony to the miracle is so solid that its falsity would be miraculous, or even more miraculous than the wondrous event?  What should a rational person conclude if he or she finds a miracle supported by absolutely incontrovertible testimony?  Is there ever such testimony for religious miracles?  Why or why not?

Long (25 minutes) essay topics (The student must select one topic):

L1.  Descartes's Method of Doubt in the First Meditation

{Why is Descartes so obsessed with doubt?  Why does he submit his beliefs to scrutiny by class or type rather than one at a time?  What causes him to doubt his sense-based beliefs?  To doubt beliefs such as that he has a head and hands?  To doubt his mathematical beliefs?  What is the Evil Demon hypothesis? What function does it serve?  Is there any way for Descartes to frustrate the Evil Demon?}

L2.  "My whole nature is to be a thinking thing" in the Second Meditation

{Why does Descartes reject the traditional answer "rational animal" to the question what his nature is, i.e., what kind of thing he is?   What is his own answer to this question?  Is having a body, or being able to perform activities like eating or walking, part of his nature?  Why or why not?  What does he mean by thinking?  Does he distinguish seeing a horse from seeming to see the horse?  Why or why not?  Is it possible that a body can think?  Is it possible that Descartes is really a body?  Which is more easily and better known: a piece of wax or one's own mind?  Why?}

L3.  The Third Meditation Argument for the Existence of God

{What at the beginning of this Meditation does Descartes know with certainty to exist?  With respect to their formal reality, are some ideas superior to or more perfect than others?  With respect to their objective reality?  What causal principle does Descartes invoke to escape from solipsism?  How does it apply to ideas?  What kind of idea will enable him to
escape solipsism?  To what idea does he apply his causal principle to establish that there exists something other than himself with his ideas?  How does his argument to the existence of God go?  Would this argument still go through if he had applied the causal principle to his idea of himself or to his idea of an angel (a purely spiritual finite substance)?  Is his idea of an infinite substance a negative or a positive idea?  Why does it matter?  Could his idea of God be materially false?  Why does it matter?}

L4.  Error, the intellect, and the will in the Fourth Meditation

{Would God be a malicious deceiver if He placed in me a cognitive faculty that makes mistakes or errors even when I use it properly?  Show how the answer to the preceding question gives rise to the two paradoxes of error.  Formulate Descartes's account of error.  Explain whether God could have given Descartes an intellect of such sort that he would never make any rors?  In what sense is Descartes's will equal to God's?  In what sense is it inferior?  Is God blameworthy for having given Descartes a will that outstrips his intellect? What can Descartes himself do to escape error?  How does he know that this
escape from error really works?  If he nonetheless falls into error, does it reflect badly on God?}

L5.  Descartes's ontological argument in the Fifth Meditation

{Where does Descartes get the idea for his ontological argument?  What is it about his idea of a triangle that makes it possible for him to prove that the sum of its interior angles equals degrees?  How does the idea of a unicorn differ from the idea of a triangle?  How cogent are mathematical demonstrations (proofs)?  Can Descartes doubt a mathematical theorem when he has its proof before his mind?  Formulate his ontological proof of the existence of God.  How cogent is it?  Why then does Descartes hesitate to accept its conclusion as an indubitable and certain truth?  Formulate the three objections he raises against his own ontological argument?  How does he answer these objections?  Does he now give his full assent to his  ontological argument and its conclusion?}

L6.  Descartes's Sixth Meditation argument to an external world

{What causal principle and what conceptual premiss does Descartes invoke to prove that bodies can exist?  Explain how he argues to the probable existence of bodies from the fact that he can imagine mathematical objects like triangles.  On the basis of what causal principle does Descartes think that his sense ideas (sensations and sense perceptions) must come from one of
these four sources: himself, bodies, God, or some being intermediate in perfection between bodies and God?  How does Descartes rule out himself as the source of his sense ideas.  Why would God be a malicious deceiver if the source of Descartes's sense ideas was either God Himself or some being intermediate between bodies and God?  What permits  Descartes now to conclude that he really does have a body and that material bodies are the sources of his adventitious sense ideas?}

Short (12 minutes each) essay topics (The student must select two of the topics below, subject to the following restriction: the short-essay topics and the long-essay topic must all pertain to different Meditations.  For example, you may choose only one of L1, S1, and S2; similarly, you may choose only one of L2, S3, and S4; and so on.}

S1.  The dream argument in the First Meditation
{Formulate Descartes's dream hypothesis.  Why does he advance it?  Which of his beliefs does it call into doubt?  Which ones does it leave intact?  Is he able to reject the dream hypothesis in this Meditation?}

S2.  The Evil Demon hypothesis in the First Meditation
{What is the Evil Demon hypothesis?  What purpose or purposes does it serve, i.e., why does Descartes introduce it?  If he  doesn't believe an Evil Demon is trying to trick him, why does he pretend that one is?  Which of Descartes's beliefs does the Evil Demon hypothesis call into doubt?  Can he avoid being deceived by the Evil Demon?  If so, how?}

S3.  "Cogito ergo sum"  ("je pense donc je suis") in the Second Meditation
{What is the Cogito, a proposition or an argument or a bit of both? How does Descartes derive it?  How certain is he that he is thinking?  How certain or indubitable is the Cogito?  How certain is Descartes that he exists?}

S4.  The piece of wax example from the Second Meditation
{Explain how Descartes uses his piece of wax example to show that mind is both better known and more easily known than body.}

S5.  Metaphysical doubt in the Third Meditation
{What is metaphysical doubt?  How does it arise?  Does it make Descartes question the Cogito?  To which of his beliefs does it apply?  Is it a serious doubt for him?  Why does he want to eliminate it?  How does he think he can eliminate it?}

S6.  Descartes's two ideas of the sun in the Third Meditation
{What are Descartes's two ideas of the sun?  Where do they appear to come from?  If an external object is the source of one of his ideas, must the idea resemble or be similar to the object?  What is the philosophical lesson of his two ideas of the sun?}

S7.  First Paradox of Error in the Fourth Meditation
{What are the premisses and conclusion of Descartes's argument that Professor Massey calls the First Paradox of Error?  Is it a satisfactory response to this argument to say that Descartes makes errors because he is an imperfect knower suspended between being and non-being?  Why or why not? Would this response be satisfactory if error were a negation  nstead of a privation?  Why or why not?}

S8.  Second Paradox of Error in the Fourth Meditation
{What are the premisses and conclusion of Descartes's argument that Professor Massey calls the Second Paradox of Error?  What is paradoxical about the conclusion?  How in brief does Descartes resolve the paradox?  Does he invoke final causes in this resolution?}

S9.  Fifth Meditation memory-of-clear-and-distinct-ideas principle
{What is the clear-and-distinct ideas principle?  What is the principle that Professor Massey calls the memory-of-clear-and-distinct-ideas principle?  Does the latter principle underwrite the former one?  What ultimately underwrites the latter principle?  What is the point or purpose of the latter principle, i.e., why does Descartes invoke it?}

S The real distinction between mind and body in the Sixth Meditation
{What is the real distinction between mind and body?  Formulate Descartes's first argument for this distinction?}

S Good-tasting poison, dropsical thirst, and God's veracity in the Sixth Meditation
{Distinguish accidental from systematic or intrinsic error?  Is the fact that someone desires to eat a good-tasting but poisoned soup an example of accidental or systematic error?  Does it convict God of malicious deception? Why or why not?  Is the illness-induced thirst of someone who suffers from dropsy an accidental or a systematic error?  If systematic, does it convict God of malicious deception?  Why or why not?}

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DESCARTES'S SIXTH MEDITATION ARGUMENT TO AN
EXTERNAL WORLD {Long Essay Topic}

1. By invoking the causal principle that God can bring about whatever Descartes can clearly and distinctly conceive in such a way that what is brought about conforms exactly to his conception of it, Descartes is able to conclude that the clarity and distinctness of his geometrical ideas shows that material bodies (real extension) can exist. It remains, however, an open question
whether they do exist.

2. Imagination and understanding are different activities. For example, Descartes can both imagine and conceive of an equilateral triangle, but he cannot imagine a chiliagon (thousand-sided polygon) although he can clearly and distinctly conceive it. Because Descartes can clearly and distinctly conceive of himself existing as a mind without the faculty of imagination,  nlyunderstanding belongs to him essentially.

3. Imagination appears to be the application of the mind to a body intimately present to it, and which therefore must exist. From the fact that there is no other account of imagination as good as the one just given, Descartes concludes that it's probable that, when he imagines something, his mind is intimately present to an actually existing body. Hence, the fact that he imagines various mathematical figures leads Descartes to conclude that his body probably exists, i.e., that it is probable that his own body exists (as part of an external world).

4. Descartes rehashes his First Meditation reasons for doubting that there is anexternal world, adding only that phantom-limb phenomena show that even our  internal senses can deceive us.

5. Because he is nothing but a mind (a thinking thing really distinct from his body), Descartes takes it for granted that he cannot himself be the source of his adventitious sense ideas (e.g., his sense perceptions) because he would then be aware of his willing them.

6. Invoking the causal principle that there must be at least as much formal reality in the cause of an idea as there is objective reality in the idea itself, Descartes concludes that his sense ideas (sense perceptions and sensations) must come from bodies, from God, or from some being intermediate in perfection between bodies and God.

7. Invoking our strong inclination to attribute many of our sensations and sense perceptions to the material bodies from which they appear to come, Descartes concludes that God would be a malicious deceiver if the source of these sensations and ideas were either God Himself or some intermediate creature more perfect than bodies, because we would then have no way to correct our strong propensity to attribute these sensations and perceptions to material bodies existing in an external world.

8. Since God is not a deceiver, Descartes concludes that he really does have a body and that material bodies are the actual sources of our sensations and sense perceptions, i.e., that his body exists (as part of an external world).

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THE REAL DISTINCTION BETWEEN MIND AND BODY IN THE
SIXTH MEDITATION {Short Essay Topic}

A. Descartes's First Argument for the Real Distinction of Mind and Body

1. What does Descartes mean when he says that x is really distinct from y?

a. That God can bring it about that x exists separately from y.

b. That x can exist apart and independently from y.

2. What causal principle does Descartes employ to establish the real distinction of mind and body?

Causal Principle: God can bring about whatever Descartes can clearly and distinctly conceive in such a way that what is brought about conforms exactly to his conception of it.

Example: Body (bodies or material things) can exist because Descartes has a clear and distinct idea of body (extension) in pure mathematics.

3. What conceptual premiss does Descartes argue from?

Conceptual Premiss: That he has a clear and distinct conception of himself as a mind (thinking substance) without a body, and of his body apart from himself as mind. That is, he can clearly and distinctly conceive of himself as a mind existing without a body, and of his body existing apart from himself as mind. (Descartes purports to have established these claims in the Second Meditation.)

4. How does the argument go?

Conceptual Premiss: Descartes has a clear and distinct conception of himself as a mind (thinking substance) without a body, and of his body apart from himself as mind. That is, he can clearly and distinctly conceive of himself as a mind existing without a body, and of his body existing apart from himself as mind.

Causal Premiss: God can bring about whatever Descartes can clearly and distinctly conceive in such a way that what is brought about conforms exactly to his conception of it.

First Conclusion: God can bring it about that Descartes is himself a mind without a body, and also bring it about that his body exists apart from him as a mind.

Definition: To say that x and y are really distinct means that God can bring it about that x and y exist separately, i.e., God can bring it about that x and y exist apart and independently.

Final Conclusion: Descartes's mind and body are really distinct.

B. Descartes's Second Argument for the Real Distinction of Mind and Body

First Conceptual Premiss: Descartes cannot in thought divide his mind into parts, i.e., he cannot conceive of his mind as divisible.

Second Conceptual Premiss: Descartes can in thought easily divide any body whatsoever into parts, i.e., he can clearly and distinctly conceive of any body as divisible.

Causal Premiss: What is divisible is really distinct from what is indivisible.

Conclusion: Descartes's mind is really distinct from his body.

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GOOD-TASTING POISON, DROPSICAL THIRST, AND GOD'S VERACITY IN THE
SIXTH MEDITATION  {Short Essay Topic}

1.  What does Descartes say that his nature, in the sense of the totality of things conferred on him by God, teaches him?  What does it appear to teach him that it really does not teach him?

Descartes says that his nature in the aforesaid sense teaches him that he has a body; that when he feels pain there is something wrong with his body; that when he is thirsty, his body needs a drink; that his mind is not present to his body as a sailor in his ship but rather that his mind is so intimately joined or fused with his body that they form a composite unit; that other bodies exist in the vicinity of his body; and that some of these other bodies should be sought out or pursued, whereas others of them should be avoided.   Descartes thinks that his nature in the aforesaid sense also appears to teach him such things as that there is absolutely nothing in a empty space (in a vacuum); that the heat or color in a body exactly resembles his ideas of the
heat and color; and that physical objects have the size and shape which they present to his senses.  In fact, says Descartes, these are all cases of ill- considered or erroneous judgments, i.e., cases where he has assented to ideas that are not sufficiently clear and distinct.

2.  What does Descartes think that his nature, in the sense of the composite of his mind and body, teaches him?  What does it appear to teach him that it really does not teach him?

Descartes thinks that his nature, considered as the composite of his mind and body, teaches him to avoid things that induce pain and to pursue things that induce pleasure.  That is to say, the natural purpose or function of his sensations and sense  erceptions is to inform him about what is beneficial and what is injurious to the composite of mind and body.  For example, his nature (as the composite of mind and body) teaches him that he should drink when he is thirsty (because his body then needs liquid), should eat when he is hungry (because his body then needs food), and should pull back his hand when it touches something that makes him feel pain (because the thing touched is harming his hand).      What nature as the composite of mind and body does not teach him, saysDescartes, is anything about the properties of objects external to him.  Truth about external objects is determined by the mind alone, not by the composite of mind and body.

3.  When someone desires to eat a sweet-smelling and sweet-tasting poison, doesn't his nature (as the composite of mind and body) make a grave error about what is beneficial to the composite?  If so, doesn't this convict the Creator of malicious deception?

The person's nature (as the composite of mind and body) teaches him to pursue the good taste, not the poison.  The fortunate fact that what tastes good is in this case also poisonous shows only that the person's nature is not omniscient; it does not show that his nature misled him, but only that it has made an accidental mistake.      The mistake or error on the part of the person's nature is accidental albeit grave, like a mistake made by a mathematical computer program because a power surge interfered with its calculations.  The mistake or error is not systematic or intrinsic, like the mistakes made by a mathematical program that has some bugs in it.  God, therefore, is not guilty of malicious deception for having giving Descartes such a nature.

4.  If God had given Descartes a nature (as a composite of mind and body) that makes systematic or intrinsic mistakes, God would be guilty of malicious deception.  But when Descartes experiences thirst when suffering from dropsy, his nature (the composite of his mind and body) is instructing him to drink because his body needs more liquid, which is simply false.  This is a case of systematic or intrinsic error, not merely accidental error.  God, therefore, is a malicious deceiver.

Descartes concedes that if God had given him a nature that makes systematic or intrinsic mistakes, God would indeed be a malicious deceiver -- but only if God could have done better.  It's true that from time to time his nature (as the composite of mind and body) does mislead him systematically or intrinsically, e.g., when thirst prompts him to drink when he is suffering
from dropsy, because what his nature then impels him to do is to consume liquid, which is in fact bad for his body in the circumstances.  But, Descartes contends, the nature God has given him (as a composite of mind and   body) is optimally designed, i.e., it is the best design possible for a creature composed of mind and body.  But no one should be blamed for doing
what is best, so God is not blameworthy for having given Descartes a nature that occasionally makes intrinsic mistakes.  God, therefore, is not a malicious deceiver.

5.  What is Descartes's argument for his claim that his nature (as a composite of mind and body) is optimally designed?

The argument runs thus:  The mind is immediately affected by only one part of the body, namely, the brain (or perhaps one particular part of the brain, viz., the pineal gland).  A state [of motion] of the brain (or of the pineal gland) sends exactly the same signals to the mind, irrespective of the states of other organs or other parts of the body.  The body is a mechanical system, so when a part A is moved by a part D by means of  intermediate parts C and B, part A would be moved exactly the same way if part D didn't move at all while parts C and B moved as before.  For example, stubbing the big toe of your left foot on a rock causes motions in the toe and foot that cause motions in the   nerves that ultimately cause a motion in the brain that affects the mind in such a way that you experience pain in your left foot, so the same motions in the nerves near your brain would cause the same brain state and thus occasion the same mental experience of pain in your left foot even if your left foot as resting comfortably on a footstool or even if your left foot had been amputated.  Experience shows that the correlation of brain
states (pineal gland states) and mental states has the following property: Of all possible mental states, each brain state occasions that particular mental state that would most benefit the mind-body composite in most of life's circumstances.  That is, for each brain state, the correlation of any other mind state with it would result in an arrangement less beneficial overall to the mind-body composite.  Thus, although the correlation of the feeling of thirst with the brain state caused by dryness of the mouth will casionally result in a desire to drink in circumstances where drinking is harmful to the body, e.g., as in a person with dropsy, in most cases where the brain is in the aforesaid state, drinking will be beneficial to the body.  Thus, the correlations of mind states with brain states in our nature (as composites of mind and body) is the best possible arrangement so far as the well being of
the mind-body composite goes.  In other words, Descartes's nature is optimally designed.

6.  Can Descartes say anything else on behalf of God's veracity?

Yes, he can and does.  Descartes points out we can correct the systematic or intrinsic errors made by our nature (as the composite of mind and body) by employing several senses instead of just one, and by using our intellect and our memory.  For example, if we suffer from dropsy, we can correct what our sensation of thirst tells us (that we need to drink) by recalling that medical science has shown that drinking is harmful to someone suffering from dropsy. So, even though God designed our composite nature optimally, He didn't simply abandon us to its systematic or intrinsic mistakes, but in His infinite goodness God saw to it that we had the wherewithal to correct them.

## 1. Conception of Knowledge

### Analysis of Knowledge

Famously, Descartes defines knowledge in terms of doubt. While distinguishing rigorous knowledge (scientia) and lesser grades of conviction (persuasio), Descartes writes:

I distinguish the two as follows: there is conviction when there remains some reason which might lead us to doubt, but knowledge is conviction based on a reason so strong that it can never be shaken by any stronger reason. ( letter to Regius, AT )

Elsewhere, while answering a challenge as to whether he succeeds in founding such knowledge, Descartes writes:

But since I see that you are still stuck fast in the doubts which I put forward in the First Meditation, and which I thought I had very carefully removed in the succeeding Meditations, I shall now expound for a second time the basis on which it seems to me that all human certainty can be founded.

First of all, as soon as we think that we correctly perceive something, we are spontaneously convinced that it is true. Now if this conviction is so firm that it is impossible for us ever to have any reason for doubting what we are convinced of, then there are no further questions for us to ask: we have everything that we could reasonably want. … For the supposition which we are making here is of a conviction so firm that it is quite incapable of being destroyed; and such a conviction is clearly the same as the most perfect certainty. (Replies 2, AT –45)

These passages (and others) clarify that Descartes understands doubt as the contrast of certainty. As my certainty increases, my doubt decreases; conversely, as my doubt increases, my certainty decreases. The requirement that knowledge is to be based in complete, or perfect certainty, amounts to requiring a complete absence of doubt — an indubitability, or inability to undermine one's conviction. Descartes' methodic emphasis on doubt, rather than on certainty, marks an epistemological innovation. This so-called ‘method of doubt’ is discussed below (Section 2).

The certainty/indubitability of interest to Descartes is psychological in character, though not merely psychological — not simply an inexplicable feeling. It has also a distinctively epistemic character, involving a kind of rational insight. During moments of certainty, it is as if my perception is guided by “a great light in the intellect” (Med. 4, AT ). This rational illumination empowers me to “see utterly clearly with my mind's eye”; my feelings of certainty are grounded — indeed, “I see a manifest contradiction” in denying the proposition of which I'm convinced. (Med. 3, AT )

Should we regard Descartes' account as a version of the justified true belief analysis of knowledge tracing back to Plato? The above texts (block quoted) are among Descartes' clearest statements concerning the brand of knowledge he seeks. Yet they raise questions about the extent to which his account is continuous with other analyses of knowledge. Prima facie, his characterizations imply a justified belief analysis of knowledge — or in language closer to his own (and where justification is construed in terms of unshakability), an unshakable conviction analysis. There's no stated requirement that the would-be knower's conviction is to be true, as opposed to being unshakably certain. Is truth, therefore, not a requirement of Descartes' brand of strict knowledge?

Many will balk at the suggestion. For in numerous texts Descartes writes about truth, even characterizing a “rule for establishing the truth” (Med. 5, AT , passim). It might therefore seem clear, whatever else is the case, that Descartes conceives of knowledge as advancing truth. Without denying this, let me play devil's advocate. It is not inconsistent to hold that we're pursuing the truth, even succeeding in establishing the truth, and yet to construe the conditions of success wholly in terms of the certainty of our conviction — i.e., wholly in terms of internalist criteria. Thus construed, to establish a proposition just is to perceive it with certainty; the result of having established it — i.e., what gets established — is the proposition's truth. Truth is a consequence of knowledge, rather than its precondition. Note again that Descartes says, of the perfect certainty he seeks, that it provides “everything that we could reasonably want,” adding (in the same passage):

What is it to us that someone may make out that the perception whose truth we are so firmly convinced of may appear false to God or an angel, so that it is, absolutely speaking, false? Why should this alleged “absolute falsity” bother us, since we neither believe in it nor have even the smallest suspicion of it? (Replies 2, AT –45)

On one reading of this remark, Descartes is explicitly embracing the consequence of having defined knowledge wholly in terms of unshakable conviction: he's conceding that achieving the brand of knowledge he seeks is compatible with being — “absolutely speaking” — in error. If this is the correct reading, the interesting upshot is that Descartes' ultimate aspiration is not absolute truth, but absolute certainty.

On a quite different reading of this passage, Descartes is clarifying that the analysis of knowledge is neutral not about truth, but about absolute truth: he's conveying that the truth condition requisite to knowledge involves truth as coherence. Harry Frankfurt defended such an interpretation in his influential work, Demons, Dreamers, and Madmen. Yet, in a follow-up paper he retracted the view:

I now think, however, that it was a mistake on my part to suggest that Descartes entertained a coherence conception of truth. The fact is that there is no textual evidence to support that suggestion; on the contrary, whenever Descartes gives an explicit account of truth he explains it unequivocally as correspondence with reality. (, 36f)

More recently, Ernest Sosa (a) and Michael Della Rocca () have helped revive interest in whether Descartes should be read as holding some form of coherence theory.

A definitive interpretation of these issues has yet to gain general acceptance in the literature. What is clear is that the brand of knowledge Descartes seeks requires, at least, unshakably certain conviction. Arguably, this preoccupation with having the right kind of certainty — including its being available to introspection — is linked with his commitment to an internalist conception of knowledge.

### Internalism and Justification

One way to divide up theories of justification is in terms of the internalism-externalism distinction. Very roughly: a theory of epistemic justification is internalist insofar as it requires that the justifying factors are accessible to the knower's conscious awareness; it is externalist insofar as it does not impose this requirement.

Descartes' internalism requires that all justifying factors take the form of ideas. For he holds that ideas are, strictly speaking, the only objects of immediate perception, or conscious awareness. (More on the directness or immediacy of perception in Section ) Independent of this theory of ideas, Descartes' methodical doubts underwrite an assumption with similar force: for almost the entirety of the Meditations, his meditator-spokesperson — hereafter referred to as the ‘meditator’ — adopts the methodological assumption that all his thoughts and experiences are occurring in a dream. This assumption is tantamount to requiring that justification come in the form of ideas.

An important consequence of this kind of interpretation — namely, a traditional representationalist reading of Descartes — is that rigorous philosophical inquiry must proceed via an inside-to-out strategy. This strategy is assiduously followed in the Meditations, and it endures as a hallmark of many early modern epistemologies. Ultimately, all judgments are grounded in an inspection of the mind's ideas. Philosophical inquiry is, properly understood, an investigation of ideas. The methodical strategy of the Meditations has the effect of forcing readers to adopt this mode of inquiry.

In recent years, some commentators have questioned this traditional way of understanding the mediating role of ideas, in Descartes' philosophy. Noteworthy is John Carriero's outstanding commentary on the Meditations (), an account providing a serious challenge to traditional representationalist interpretations (as are often assumed in the present treatment).

### Indefeasibility in Context

In characterizing knowledge as “incapable of being destroyed,” Descartes portrays knowledge as enduring. Our conviction must be, he writes, “so strong that it can never be shaken”; “so firm that it is impossible for us ever to have any reason for doubting.” Descartes wants a brand of certainty/indubitability that is of the highest rank, both in terms of degree and durability. He wants knowledge that is utterly indefeasible. (Sceptical doubts count as defeaters.)

This indefeasibility requirement implies more than mere stability. A would-be knower could achieve stability simply by never reflecting on reasons for doubt. But this would result in mere undoubtedness, not indubitability. Referring to such a person, Descartes points out that although a reason for “doubt may not occur to him, it can still crop up if someone else raises the point or if he looks into the matter himself” (Replies 2, AT ).

Many readers conclude that Descartes' standards of justification are too high, for they have the consequence that almost nothing we ordinarily count as knowledge measures up. Before jumping to this conclusion, we should put the indefeasibility requirement into context.

Descartes is a contextualist in the sense that he allows that different standards of justification are appropriate to different contexts. This is not merely to say the obvious: that depending on the context of inquiry, knowledge-worthy justification will sometimes be needed, but other times not. It's to say something stronger: that depending on the context of inquiry, the standards of knowledge-worthy justification might vary. For example, a contextualist might accept that ‘knowledge’-talk is equally appropriate whether one is describing the best achievements of empirical science, or the best achievements of mathematics, while acknowledging that the former rest on weaker standards of proof than the latter. This example is potentially misleading, in that Descartes appears loath to count mere empirical evidence as knowledge-worthy justification. But upon ramping up the standard to what he finds minimally acceptable, the standard admits of context dependent variation.

Descartes' minimum standard targets the level of certainty arising when the mind's perception is both clear and distinct. (For Descartes, clarity contrasts with obscurity, and distinctness contrasts with confusion.) He allows that judgments grounded in clear and distinct perception are defeasible (at least, for those who've not yet read the Meditations). But he regularly characterizes defeasible judgments at this level of certainty using terminology (e.g., ‘cognitio’ and its cognates) that translates well into the English ‘knowledge’ (and its cognates).

In the context of inquiry at play in the Meditations, Descartes insists on indefeasibility. (Typically, he reserves the term ‘scientia’ for this brand of knowledge, though he uses ‘cognitio’ and its cognates for either context.) Descartes' aim is, once and for all, to lay a lasting foundation for knowledge. To achieve this, he contends that we “cannot possibly go too far in [our] distrustful attitude” (Med. 1, AT ). Better to have a standard that excludes some truths, than one that justifies some falsehoods.

An interesting thesis emerges — call it the ‘No Atheistic Knowledge Thesis’. Descartes maintains that though atheists are quite capable of impressive knowledge, including in mathematics, they are incapable of the indefeasible brand of knowledge he seeks:

The fact that an atheist can be “clearly aware [clare cognoscere] that the three angles of a triangle are equal to two right angles” is something I do not dispute. But I maintain that this awareness [cognitionem] of his is not true knowledge [scientiam], since no act of awareness [cognitio] that can be rendered doubtful seems fit to be called knowledge [scientia]. Now since we are supposing that this individual is an atheist, he cannot be certain that he is not being deceived on matters which seem to him to be very evident (as I fully explained). (Replies 2, AT )

Hereafter, let us refer to the indefeasible brand of knowledge Descartes seeks as ‘Knowledge’ (uppercase ‘K’).

### Methodist Approach

How is the would-be Knower to proceed in identifying candidates for Knowledge? Distinguish particularist and methodist responses to the question. The particularist is apt to trust our prima facie intuitions regarding particular knowledge claims. These intuitions may then be used to help identify more general epistemic principles. The methodist, in contrast, is apt to distrust our prima facie intuitions. The preference is instead to begin with general principles about proper method. The methodical principles may then be used to arrive at settled, reflective judgments concerning particular knowledge claims.

Famously, Descartes is in the methodist camp. Those who haphazardly “direct their minds down untrodden paths” are sometimes “lucky enough in their wanderings to hit upon some truth,” but “it is far better,” writes Descartes, “never to contemplate investigating the truth about any matter than to do so without a method” (Rules 4, AT ). Were we to rely on our prima facie intuitions, we might suppose it obvious that the earth is unmoved, or that ordinary objects (as tables and chairs) are just as just as they seem. Yet, newly emerging mechanist doctrines of the 17th century imply that these suppositions are false. Such cases underscore the unreliability of our prima facie intuitions and the need for a method by which to distinguish truth and falsity.

Descartes' view is not that all our pre-reflective intuitions are mistaken. He concedes that “no sane person has ever seriously doubted” such particular claims as “that there really is a world, and that human beings have bodies” (Synopsis, AT ). But such pre-reflective judgments may be ill-grounded, even when true.

The dialectic of the First Meditation features a confrontation between particularism and methodism, with methodism emerging the victor. For example, the meditator (while voicing empiricist sensibilities) puts forward, as candidates for the foundations of Knowledge, such prima facie obvious claims as “that I am here, sitting by the fire, wearing a winter dressing-gown, holding this piece of paper in my hands, and so on” — particular matters “about which doubt is quite impossible,” or so it would seem (AT ). In response (and at each level of the dialectic), Descartes invokes his own methodical principles to show that the prima facie obviousness of such particular claims is insufficient to meet the burden of proof.

### Innate Ideas

Descartes' commitment to innate ideas places him in a rationalist tradition tracing back to Plato. Knowledge of the nature of reality derives from ideas of the intellect, not the senses. An important part of metaphysical inquiry therefore involves learning to think with the intellect. Plato's allegory of the cave portrays this rationalist theme in terms of epistemically distinct worlds: what the senses reveal is likened to shadowy imagery on the wall of a poorly lit cave; what the intellect reveals is likened to a world of fully real beings illuminated by bright sunshine. The metaphor aptly depicts our epistemic predicament given Descartes' own doctrines. An important function of his methods is to help would-be Knowers redirect their attention from the confused imagery of the senses to the luminous world of the intellect's clear and distinct ideas.

Further comparisons arise with Plato's doctrine of recollection. The Fifth Meditation meditator remarks — having applied Cartesian methodology, thereby discovering innate truths within: “on first discovering them it seems that I am not so much learning something new as remembering what I knew before” (Med. 5, AT ). Elsewhere Descartes adds, of innate truths:

[W]e come to know them by the power of our own native intelligence, without any sensory experience. All geometrical truths are of this sort — not just the most obvious ones, but all the others, however abstruse they may appear. Hence, according to Plato, Socrates asks a slave boy about the elements of geometry and thereby makes the boy able to dig out certain truths from his own mind which he had not previously recognized were there, thus attempting to establish the doctrine of reminiscence. Our knowledge of God is of this sort. ( letter To Voetius, AT 8b–67)

The famous wax thought experiment of the Second Meditation is supposed to illustrate (among other things) a procedure to “dig out” what is innate. The thought experiment purports to help the meditator achieve a “purely mental scrutiny,” thereby apprehending more easily the innate idea of body. (Med. 2, AT –31) According to Descartes, our minds come stocked with a variety of intellectual concepts — ideas whose content is independent of experience. This storehouse includes ideas in mathematics, logic, and metaphysics. Interestingly, Descartes holds that even our sensory ideas involve innate content. On his understanding of the new mechanical physics, bodies have no real properties resembling our sensory ideas of colors, sounds, tastes, and the like, thus implying that the content of such ideas draws from the mind itself. But if even these sensory ideas count as innate, how then are we to characterize the doctrine of innateness? Importantly, the formation of these sensory ideas — unlike purely intellectual concepts — depends on sensory stimulation. On one plausible understanding, Descartes' official doctrine has it that ideas are innate insofar as their content derives from the nature of the mind alone, as opposed to deriving from sense experience (cf. Newman ). This characterization allows that both intellectual and sensory concepts draw on native resources, though not to the same extent.

Though the subject of rationalism in Descartes' epistemology deserves careful attention, the present article generally focuses on Descartes' efforts to achieve indefeasible Knowledge. Relatively little attention is given to his doctrines of innateness, or, more generally, his ontology of thought.

Further reading: For a contrary understanding of Descartes' conception of scientia, see Jolley (). On the internalism-externalism distinction, see Alston () and Plantinga (). For a partly externalist interpretation of Descartes, see Della Rocca (). For coherentist interpretations of Descartes' project, see Frankfurt (), Sosa (a), and Della Rocca (); for a reply to such interpretations, see Frankfurt () and Newman (). For a stability interpretation of Descartes, see Bennett(). On the indefeasibility of Knowledge, see Newman and Nelson (). On contextualism in Descartes, see Newman (). On the methodism-particularism distinction, see Chisholm () and Sosa (). On analysis and synthesis, see Smith (). On Descartes' rationalism, see Adams (), Jolley (), Newman (), and Nelson ().

## 2. Methods: Foundationalism and Doubt

Of his own methodology, Descartes writes:

Throughout my writings I have made it clear that my method imitates that of the architect. When an architect wants to build a house which is stable on ground where there is a sandy topsoil over underlying rock, or clay, or some other firm base, he begins by digging out a set of trenches from which he removes the sand, and anything resting on or mixed in with the sand, so that he can lay his foundations on firm soil. In the same way, I began by taking everything that was doubtful and throwing it out, like sand … (Replies 7, AT )

The theory whereby items of knowledge are best organized on an analogy to architecture traces back to ancient Greek thought — to Aristotle, and to work in geometry. That Descartes' method effectively pays homage to Aristotle is, of course, welcome by his Aristotelian audience. But Descartes views Aristotle's foundationalist principles as incomplete, at least when applied to metaphysical inquiry. His method of doubt is intended to complement foundationalism. The two methods are supposed to work in cooperation, as conveyed in the above quotation. Let's consider each method.

### Foundationalism

The central insight of foundationalism is to organize knowledge in the manner of a well-structured, architectural edifice. Such an edifice owes its structural integrity to two kinds of features: a firm foundation and a superstructure of support beams firmly anchored to the foundation. A system of justified beliefs might be organized by two analogous features: a foundation of unshakable first principles, and a superstructure of further propositions anchored to the foundation via unshakable inference.

Exemplary of a foundationalist system is Euclid's geometry. Euclid begins with a foundation of first principles — definitions, postulates, and axioms or common notions — on which he then bases a superstructure of further propositions. Descartes' own designs for metaphysical Knowledge are inspired by Euclid's system:

Those long chains composed of very simple and easy reasoning, which geometers customarily use to arrive at their most difficult demonstrations, had given me occasion to suppose that all the things which can fall under human knowledge are interconnected in the same way. (Discourse 2, AT ).

It would be misleading to characterize the arguments of the Meditations as unfolding straightforwardly according to geometric method. But Descartes maintains that they can be reconstructed as such, and he expressly does so at the end of the Second Replies — providing a “geometrical” exposition of his central constructive steps, under the following headings: definitions, postulates, axioms or common notions, and propositions (AT ff).

As alluded to above, the Meditations contains a destructive component that Descartes likens to the architect's preparations for laying a foundation. Though the component finds no analogue in the method of the geometers, Descartes appears to hold that this component is needed in metaphysical inquiry. The discovery of Euclid's first principles (some of them, at any rate) is comparatively unproblematic: such principles as that things which are equal to the same thing are also equal to one another (one of Euclid's axioms) accord not only with reason, but with the senses. In contrast, metaphysical inquiry might have first principles that conflict with the senses:

The difference is that the primary notions which are presupposed for the demonstration of geometrical truths are readily accepted by anyone, since they accord with the use of our senses. Hence there is no difficulty there, except in the proper deduction of the consequences, which can be done even by the less attentive, provided they remember what has gone before. … In metaphysics by contrast there is nothing which causes so much effort as making our perception of the primary notions clear and distinct. Admittedly, they are by their nature as evident as, or even more evident than, the primary notions which the geometers study; but they conflict with many preconceived opinions derived from the senses which we have got into the habit of holding from our earliest years, and so only those who really concentrate and meditate and withdraw their minds from corporeal things, so far as possible, will achieve perfect knowledge of them. (Replies 2, AT –57)

Among Descartes' persistent themes is that such preconceived opinions can have the effect of obscuring our mental vision of innate principles; that where there are disputes about first principles, it is not “because one man's faculty of knowledge extends more widely than another's, but because the common notions are in conflict with the preconceived opinions of some people who, as a result, cannot easily grasp them”; whereas, “we cannot fail to know them [innate common notions] when the occasion for thinking about them arises, provided that we are not blinded by preconceived opinions” (Prin. –50, AT 8a). These “preconceived opinions” must be “set aside,” says Descartes, “in order to lay the first foundations of philosophy” ( letter to Voetius, AT 8b). Unless they are set aside, we're apt to regard — as first principles — the mistaken (though prima facie obvious) sensory claims that particularists find attractive. Such mistakes in the laying of the foundations weaken the entire edifice. Descartes adds:

All the mistakes made in the sciences happen, in my view, simply because at the beginning we make judgements too hastily, and accept as our first principles matters which are obscure and of which we do not have a clear and distinct notion. (Search, AT )

Though foundationalism brilliantly allows for the expansion of knowledge from first principles, Descartes thinks that a complementary method is needed to help us discover genuine first principles. As Gary Hatfield writes, “the problem is not to carry out proofs (which might well be assented to, given the definitions and axioms), but to discover the axioms themselves, (which are hopelessly obscured by the prejudices of the senses)” (, 71). Descartes therefore devises the method of doubt for this purpose — a method to help “set aside” preconceived opinions.

### Method of Doubt

Descartes opens the First Meditation asserting the need “to demolish everything completely and start again right from the foundations” (AT ). The passage adds:

Reason now leads me to think that I should hold back my assent from opinions which are not completely certain and indubitable just as carefully as I do from those which are patently false. So, for the purpose of rejecting all my opinions, it will be enough if I find in each of them at least some reason for doubt. (AT )

In the architectural analogy, we can think of bulldozers as the ground clearing tools of demolition. For Knowledge building, Descartes construes sceptical doubts as the ground clearing tools of epistemic demolition. Bulldozers undermine literal ground; doubt undermines epistemic ground. Using sceptical doubts, the meditator shows us how to find “some reason for doubt” in all our preexisting opinions.

Descartes' ultimate aims, however, are constructive. Unlike “the sceptics, who doubt only for the sake of doubting,” Descartes aims “to reach certainty — to cast aside the loose earth and sand so as to come upon rock or clay” (Discourse 3, AT –29). Bulldozers are typically used for destructive ends, as are sceptical doubts. Descartes' methodical innovation is to employ demolition for constructive ends. Where a bulldozer's force overpowers the ground, its effects are destructive. Where the ground's firmness resists the bulldozer's force, the bulldozer might be used constructively — using it to reveal the ground as firm. Descartes' innovation is to use epistemic bulldozers in this way. He uses sceptical doubts to test the firmness of candidates put forward for the foundations of Knowledge.

According to at least one prominent critic, this employment of sceptical doubt is unnecessary and excessive. Writes Gassendi:

There is just one point I am not clear about, namely why you did not make a simple and brief statement to the effect that you were regarding your previous knowledge as uncertain so that you could later single out what you found to be true. Why instead did you consider everything as false, which seems more like adopting a new prejudice than relinquishing an old one? This strategy made it necessary for you to convince yourself by imagining a deceiving God or some evil demon who tricks us, whereas it would surely have been sufficient to cite the darkness of the human mind or the weakness of our nature. (Objs. 5, AT –58; my italics)

Here, Gassendi singles out two features of methodic doubt — its universal and hyperbolic character. In reply, Descartes remarks:

You say that you approve of my project for freeing my mind from preconceived opinions; and indeed no one can pretend that such a project should not be approved of. But you would have preferred me to have carried it out by making a “simple and brief statement” — that is, only in a perfunctory fashion. Is it really so easy to free ourselves from all the errors which we have soaked up since our infancy? Can we really be too careful in carrying out a project which everyone agrees should be performed? (Replies 5, AT )

Evidently, Descartes holds that the universal and hyperbolic character of methodic doubt is helpful to its success. Further appeal to the architectural analogy helps elucidate why. Incorporating these features enables the method to more effectively identify first principles. Making doubt universal and hyperbolic helps to distinguish genuine unshakability from the mere appearance of it.

Consider first the universal character of doubt — the need “to demolish everything completely and start again right from the foundations” (Med. 1, AT ). The point is not merely to apply doubt to all candidates for Knowledge, but to apply doubt collectively. Descartes offers the following analogy:

Suppose [a person] had a basket full of apples and, being worried that some of the apples were rotten, wanted to take out the rotten ones to prevent the rot spreading. How would he proceed? Would he not begin by tipping the whole lot out of the basket? And would not the next step be to cast his eye over each apple in turn, and pick up and put back in the basket only those he saw to be sound, leaving the others? In just the same way, those who have never philosophized correctly have various opinions in their minds which they have begun to store up since childhood, and which they therefore have reason to believe may in many cases be false. They then attempt to separate the false beliefs from the others, so as to prevent their contaminating the rest and making the whole lot uncertain. Now the best way they can accomplish this is to reject all their beliefs together in one go, as if they were all uncertain and false. They can then go over each belief in turn and re-adopt only those which they recognize to be true and indubitable. (Replies 7, AT )

That even one falsehood would be mistakenly treated as a genuine first principle — say, the belief that the senses are reliable, or that ancient authorities should be trusted — threatens to spread falsehood to other beliefs in the system. A collective doubt helps avoid such mistakes. It ensures that the method only approves candidate first principles that are unshakable in their own right: it rules out that the appearance of unshakability is owed to logical relations with other principles, themselves not subjected to doubt.

How is the hyperbolic character of methodic doubt supposed to contribute to the method's success? The architectural analogy is again helpful. Suppose that an architect is vigilant in employing a universal/collective doubt. Suppose, further, that she attempts to use bulldozers for constructive purposes. A problem nonetheless arises. How big a bulldozer is she to use? A light-duty bulldozer might be unable to distinguish a medium-sized boulder, and immovable bedrock. In both cases, the ground would appear immovable. The solution lies in using not light-duty, but heavy-duty tools of demolition — the bigger the bulldozer, the better. The lesson is clear for the epistemic builder: the more hyperbolic the doubt, the better.

A potential problem remains. Does not the problem of the “light-duty bulldozer” repeat itself? No matter how firm one's ground, might it not be dislodged in the face of a yet bigger bulldozer? This raises the worry that there might not be unshakable ground, as opposed to ground which is yet unshaken. Descartes' goal of utterly indubitable epistemic ground may simply be elusive.

Perhaps the architectural analogy breaks down in a manner that serves Descartes well. For though there is no most-powerful literal bulldozer, perhaps epistemic bulldozing is not subject to this limitation. Descartes seems to think that there is a most-powerful doubt — a doubt than which none more hyperbolic can be conceived. The Evil Genius Doubt (and equivalent doubts) is supposed to fit the bill. If the method reveals epistemic ground that stands fast in the face of a doubt this hyperbolic, then, as Descartes seems to hold, this counts as epistemic bedrock if anything does.

Hence the importance of the universal and hyperbolic character of the method of doubt. Gassendi's suggestion that we forego methodic doubt in favor of a “simple and brief statement to the effect that [we're] regarding [our] previous knowledge as uncertain” misses the intended point of methodic doubt.

Descartes' method of doubt has been subject to numerous objections — some fair, others less so. Rendered in the terms Descartes himself employs, the method is arguably less flawed than its reputation. Let us consider some of the common objections. Two such objections are suggested in a passage from the pragmatist Peirce:

We cannot begin with complete doubt. We must begin with all the prejudices which we actually have when we enter upon the study of philosophy. These prejudices are not to be dispelled by a maxim [viz., the maxim that the philosopher “must begin with universal doubt”], for they are things which it does not occur to us can be questioned. Hence this initial skepticism will be a mere self-deception, and not real doubt … A person may, it is true, in the course of his studies, find reason to doubt what he began by believing; but in that case he doubts because he has a positive reason for it, and not on account of the Cartesian maxim. Let us not pretend to doubt in philosophy what we do not doubt in our hearts. (, f)

The procedure of the Meditations is not that universal doubt is supposed to flow simply from adherence to a maxim; to the contrary, the doubt is supposed to flow from careful attention to positive reasons for doubt. Descartes introduces sceptical arguments precisely in acknowledgement that we need such reasons:

I did say that there was some difficulty in expelling from our belief everything we have previously accepted. One reason for this is that before we can decide to doubt, we need some reason for doubting; and that is why in my First Meditation I put forward the principal reasons for doubt. (Replies 5, appendix, AT 9a)

A second objection is suggested by Peirce's reference to a “doubt in our hearts.” Distinguish two kinds of doubt, in terms of two kinds of ways that doubt can defeat knowledge. Some doubts purport to undermine one's conviction or belief — call these ‘belief-defeating doubts’. Other doubts purport to undermine one's justification (whether or not they undermine belief) — call these ‘justification-defeating doubts’. What Peirce calls a ‘doubt in our hearts’ is suggestive of a belief-defeating doubt. Is Peirce therefore right that only belief-defeating doubts can undermine knowledge? Longstanding traditions in philosophy acknowledge that there may be truths we believe in our hearts (as it were), but which we do not know. This is one of the intended lessons of methodic doubt. The sceptical scenarios are supposed to help us appreciate that though we believe that 2+3=5, and believe that we're awake, and believe that there is an external world, we may nonetheless lack Knowledge. As already noted, Descartes writes — of external world doubts — that “no sane person has ever seriously doubted” such matters. Justification-defeating doubts are sufficient to undermine Knowledge, and this is the sort of doubt that Descartes puts forward.

A related objection has the method calling not merely for doubt, but for disbelief or dissent. One of Gassendi's objections reads in this manner. He seems to take Descartes to be urging us, quite literally, to “consider everything as false,” a strategy which, as he says to Descartes, “made it necessary for you to convince yourself” of the sceptical hypotheses (Objs. 5, AT –58). Based on Descartes' most careful statements, however, his method does not require us to dissent from the beliefs it undermines. Rather, the method urges us to “hold back [our] assent from opinions which are not completely certain and indubitable just as carefully as [we] do from those which are patently false” (Med. 1, AT , cf. AT ).

Finally, a common objection has it that the universality of doubt undermines the method of doubt itself, since, for example, the sceptical hypotheses themselves are so dubious. Descartes thinks this misses the point of the method: namely, to extend doubt universally to candidates for Knowledge, but not also to the very tools for founding Knowledge. As he concedes: “there may be reasons which are strong enough to compel us to doubt, even though these reasons are themselves doubtful, and hence are not to be retained later on” (Replies 7, AT –74).

Further reading: On foundationalism: for Descartes' treatment, see Discourse, First Meditation, and Seventh Objections and Replies; for its treatment by ancients, see Euclid () and Aristotle (Posterior Analytics); by interpreters of Descartes, see Sosa (a) and Van Cleve (). On Cartesian inference, see Gaukroger () and Hacking (). On methodical doubt: for Descartes' treatment, see Rules, Discourse, First Meditation, and Seventh Replies; by commentators, see Frankfurt (), Garber (), Newman (), Williams (), and Wilson (). On needing reasons for doubt (contrary to direct voluntarism), see Newman (). On the analysis-synthesis distinction (closely related to issues of doubt and methodology): see the Second Replies (AT ff); see also Galileo (, 50f), Arnauld (, –3), Curley (), and Hintikka ().

## 3. First Meditation Doubting Arguments

### Dreaming Doubt

Historically, there are at least two distinct dream-related doubts. The one doubt undermines the judgment that I am presently awake — call this the ‘Now Dreaming Doubt’. The other doubt undermines the judgment that I am ever awake (i.e., in the way normally supposed) — call this the ‘Always Dreaming Doubt’. A textual case can be made on behalf of both formulations being raised in the Meditations.

Both doubts appeal to some version of the thesis that the experiences we take as dreams are (at their best) qualitatively similar to those we take as waking — call this the ‘Similarity Thesis’. The Similarity Thesis may be formulated in a variety of strengths. A strong Similarity Thesis might contend that some dreams are experientially indistinguishable from waking, even subsequent to waking-up; a weaker thesis might contend merely that dreams seem similar to waking while having them, but not upon waking. Debates about precisely how similar waking and dreaming can be, have raged for more than two millennia. The tone of the debates suggests that the degree of qualitative similarity may vary across individuals (or, at least, across their recollections of dreams). Granting such variation, dreaming doubts that depend on weaker versions of the Similarity Thesis are (other things equal) apt to be more persuasive. Let us consider a textually defensible formulation that is relatively weak. (Note, however, that some texts suggest a strong thesis: “As if I did not remember other occasions when I have been tricked by exactly similar thoughts while asleep” (Med. 1, AT ).)

The relatively weak thesis is this: that the similarity between waking and dreaming is sufficient to render it thinkable that a dream experience would seem realistic, even when reflecting on the experience, while having it. As Descartes writes: “every sensory experience I have ever thought I was having while awake I can also think of myself as sometimes having while asleep” (Med. 6, AT ). This version of the Similarity Thesis is endorsable by those who never recollect dreams that seem, on hindsight, experientially indistinguishable from waking; indeed, it's perhaps endorsable even by those who simply do not remember their dreams to any significant degree.

This weak Similarity Thesis is sufficient to generate straightaway the Now Dreaming Doubt. Since it is thinkable that a dream would convincingly seem as realistic (while having it) as my present experience seems, then, for all I Know, I am now dreaming.

Recall that Descartes' method requires only a justification-defeating doubt, not a belief-defeating doubt. The method requires me to appreciate that my present belief (that I'm awake) is not sufficiently justified. It does not require that I give up that belief. (I might continue to hold it on some merely psychological grounds.) Nor does the belief need to be false — I might, in fact, be awake. The Now Dreaming Doubt does its epistemic damage so long as it undermines my reasons for believing I'm awake — i.e., so long as I find it thinkable that a dream would seem this good. The First Meditation makes a case that this is indeed thinkable. As Descartes writes: “there are never any sure signs by means of which being awake can be distinguished from being asleep” (Med. 1, AT ).

The conclusion — that I don't Know that I'm now awake — has widespread sceptical consequences. For if I don't Know this, then neither do I Know that I'm now “holding this piece of paper in my hands,” to cite an example the meditator had supposed to be “quite impossible” to doubt. Reflection on the Now Dreaming Doubt changes his mind. He comes around to the view that, for all he Knows, the sensible objects of his present experience are mere figments of a vivid dream.

Much ado has been made about whether dreaming arguments are self-refuting. According to an influential objection, similarity theses presuppose that we can reliably distinguish dreams and waking, yet the conclusion of dreaming arguments presupposes that we cannot. Therefore, if the conclusion of such an argument is true, then the premise stating the Similarity Thesis cannot be. Some formulations of the thesis do make this mistake. Of present interest is whether all do — specifically, whether Descartes makes the mistake. He does not. Interestingly, his formulation presupposes simply the truism that we do in fact distinguish dreaming and waking (never mind whether reliably). He states his version of the thesis in terms of what we think of as dreams, versus what we think of as waking: “every sensory experience I have ever thought I was having while awake I can also think of myself as sometimes having while asleep” (Med. 6, AT ). This formulation avoids the charge of self-refutation, for it is compatible with the conclusion that we cannot reliably distinguish dreams and waking.

Does Descartes also put forward a second dreaming argument, the Always Dreaming Doubt? There is strong textual evidence to support this (see Newman ), though it is by no means the standard interpretation. The conclusion of the Always Dreaming Doubt is generated from the very same Similarity Thesis, together with a further sceptical assumption, namely: that for all I Know, the processes producing what I take as waking are no more veridical than those producing what I take as dreams. As Descartes writes:

[E]very sensory experience I have ever thought I was having while awake I can also think of myself as sometimes having while asleep; and since I do not believe that what I seem to perceive in sleep comes from things located outside me, I did not see why I should be any more inclined to believe this of what I think I perceive while awake. (Med. 6, AT )

The aim of the Always Dreaming Doubt is to undermine not whether I'm now awake, but whether so-called “sensation” is produced by external objects even on the assumption that I am now awake. For in the cases of both waking and dreaming, my cognitive access extends only to the productive result, but not the productive process. On what basis, then, do I conclude that the productive processes are different — that external objects play more of a role in waking than in dreaming? For all I Know, both sorts of experience are produced by some subconscious faculty of my mind. As Descartes has his meditator say:

[T]here may be some other faculty [of my mind] not yet fully known to me, which produces these ideas without any assistance from external things; this is, after all, just how I have always thought ideas are produced in me when I am dreaming. (Med. 3, AT )

The sceptical consequences of the Always Dreaming Doubt are even more devastating than those of the Now Dreaming Doubt. If I do not Know that “normal waking” experience is produced by external objects, then, for all I Know, all of my experiences might be dreams of a sort. For all I Know, there might not be an external world. My best evidence of an external world derives from my preconceived opinion that external world objects produce my waking experiences. Yet the Always Dreaming Doubt calls this into question:

All these considerations are enough to establish that it is not reliable judgement but merely some blind impulse that has made me believe up till now that there exist things distinct from myself which transmit to me ideas or images of themselves through the sense organs or in some other way. (Med. 3, AT –40)

The two dreaming doubts are parasitic on the same Similarity Thesis, though their sceptical consequences differ. The Now Dreaming Doubt raises the universal possibility of delusion: for any one of my sensory experiences, it is possible (for all I Know) that the experience is delusive. The Always Dreaming Doubt raises the possibility of universal delusion: it is possible (for all I Know) that all my sensory experiences are delusions (say, from a God's-eye perspective).

### Evil Genius Doubt

Though dreaming doubts do significant demolition work, they are light-duty bulldozers relative to Descartes' most power sceptical doubt. What further judgments are left to be undermined? Following the discussion of dreaming, the meditator tentatively concludes that the results of empirical disciplines “are doubtful” — e.g., “physics, astronomy, medicine,” and the like. Whereas:

[A]rithmetic, geometry and other subjects of this kind, which deal only with the simplest and most general things, regardless of whether they really exist in nature or not, contain something certain and indubitable. For whether I am awake or asleep, two and three added together are five, and a square has no more than four sides. It seems impossible that such transparent truths should incur any suspicion of being false. (Med. 1, AT )

In the final analysis, Descartes holds that such transparent truths — along with demonstrable truths, and many judgments of internal sense — are indeed Knowable. To become actually Known, however, they must stand unshakable in the face the most powerful of doubts. The stage is thus set for the introduction of another sceptical hypothesis.

The most famous rendering of Descartes' most hyperbolic doubt takes the form of the Evil Genius Doubt. Suppose I am the creation of a powerful but malicious being. This “evil genius” (or deceiving “God, or whatever I may call him,” AT ) has given me flawed cognitive faculties, such that I am in error even about epistemically impressive matters — even the simple matters that seem supremely evident. The suggestion is perhaps unbelievable, but not unthinkable. It is intended as a justification-defeating doubt that undermines our judgments about even the most simple and evident matters.

Many readers of Descartes assume that the Evil Genius Doubt draws its sceptical force from the “utmost power” attributed to the deceiver. This is to misunderstand Descartes. He contends that an equally powerful doubt may be generated on the opposite supposition — namely, the supposition that I am not the creature of an all-powerful being:

Perhaps there may be some who would prefer to deny the existence of so powerful a God rather than believe that everything else is uncertain. … yet since deception and error seem to be imperfections, the less powerful they make my original cause, the more likely it is that I am so imperfect as to be deceived all the time. (Med. 1, AT ).

Descartes makes essentially the same point in a parallel passage of the Principles:

[W]e have been told that there is an omnipotent God who created us. Now we do not know whether he may have wished to make us beings of the sort who are always deceived even in those matters which seem to us supremely evident … We may of course suppose that our existence derives not from a supremely powerful God but either from ourselves or from some other source; but in that case, the less powerful we make the author of our coming into being, the more likely it will be that we are so imperfect as to be deceived all the time. (Prin. , AT 8a:6)

Descartes' official position is that the Evil Genius Doubt is merely one among multiple hypotheses that can motivate the more general hyperbolic doubt. Fundamentally, the doubt is about my cognitive nature — about the possibility that my mind is flawed. Descartes consistently emphasizes this theme throughout the Meditations (italics added):

God could have given me a nature such that I was deceived even in matters which seemed most evident. (Med. 3, AT )

I can convince myself that I have a natural disposition to go wrong from time to time in matters which I think I perceive as evidently as can be. (Med. 5, AT )

I saw nothing to rule out the possibility that my natural constitution made me prone to error even in matters which seemed to me most true. (Med. 6, AT )

What is essential to the doubt is not a specific story about how I got my cognitive wiring; it's instead the realization — regardless the story — that, for all I Know, my cognitive wiring is flawed. In this vein, Carriero helpfully refers to the doubt under the heading, ‘imperfect-nature doubt’ (, 27). Even so, I regularly speak in terms of the evil genius (following Descartes' lead), as a kind of mnemonic for the more general doubt about our cognitive nature.

Having introduced the Evil Genius Doubt, the First Meditation program of demolition is not only hyperbolic but universal. As the meditator remarks, I “am finally compelled to admit that there is not one of my former beliefs about which a doubt may not properly be raised” (Med. 1, AT ). As will emerge, the early paragraphs of the Third Meditation clarify a further nuance of the Evil Genius Doubt — a nuance consistently observed thereafter. Descartes clarifies, there, that the Evil Genius Doubt operates in an indirect manner, a topic to which we return (in Section ).

Further reading: On Descartes' sceptical arguments, see Bouwsma (), Curley (), Larmore (), Newman (), Newman and Nelson (), Williams ( and ). For a contrary reading of the Evil Genius Doubt, see Gewirth () and Wilson (). For a more general philosophical treatment of dreaming arguments, see Dunlap () and Williams ().

## 4. Cogito Ergo Sum

### The First Item of Knowledge

Famously, Descartes puts forward a very simple candidate as the “first item of knowledge.” The candidate is suggested by methodic doubt — by the very effort at thinking all my thoughts might be mistaken. Early in the Second Meditation, Descartes has his meditator observe:

I have convinced myself that there is absolutely nothing in the world, no sky, no earth, no minds, no bodies. Does it now follow that I too do not exist? No: if I convinced myself of something then I certainly existed. But there is a deceiver of supreme power and cunning who is deliberately and constantly deceiving me. In that case I too undoubtedly exist, if he is deceiving me; and let him deceive me as much as he can, he will never bring it about that I am nothing so long as I think that I am something. So after considering everything very thoroughly, I must finally conclude that this proposition, I am, I exist, is necessarily true whenever it is put forward by me or conceived in my mind. (Med. 2, AT )

As the canonical formulation has it, I think therefore I am. (Latin: cogito ergo sum; French: je pense, donc je suis.) This formulation does not expressly arise in the Meditations.

Descartes regards the ‘cogito’ (as it is standardly referred to) as the “first and most certain of all to occur to anyone who philosophizes in an orderly way” (Prin. , AT 8a:7). Is the great certainty of the cogito supposed to attach to the “I think,” the “I am,” or the “therefore” (i.e., their logical relation)? Presumably, it must attach to all of these, if the cogito is to play the foundational role Descartes assigns to it. But this answer depends on whether the cogito is understood as an inference or an intuition — an issue addressed below.

Testing the cogito by means of methodic doubt is supposed to reveal its unshakable certainty. As earlier noted, the existence of my body is subject to doubt. The existence of my thinking, however, is not. The very attempt at thinking away my thinking is indeed self-stultifying.

The cogito raises numerous philosophical questions and has generated an enormous literature. Let us try, in summary fashion, to clarify a few central points.

First, a first-person formulation is essential to the certainty of the cogito. Third-person claims, such as “Icarus thinks,” or “Descartes thinks,” are not unshakably certain — not for me, at any rate; only the occurrence of my thought has a chance of resisting hyperbolic doubt. There are a number of passages in which Descartes refers to a third-person version of the cogito. But none of these occurs in the context of establishing the actual existence of a particular thinker (in contrast with the conditional, general result that whatever thinks exists).

Second, a present tense formulation is essential to the certainty of the cogito. It's no good to reason that “I existed last Tuesday, since I recall my thinking on that day.” For all I Know, I'm now merely dreaming about that occasion. Nor does it work to reason that “I'll continue to exist, since I'm now thinking.” As the meditator remarks, “it could be that were I totally to cease from thinking, I should totally cease to exist” (Med. 2, AT ). The privileged certainty of the cogito is grounded in the “manifest contradiction” (cf. AT ) of trying to think away my present thinking.

Third, the certainty of the cogito depends on being formulated in terms of my cogitatio — i.e., my thinking, or awareness/consciousness more generally. Any mode of thinking is sufficient, including doubting, affirming, denying, willing, understanding, imagining, and so on (cf. Med. 2, AT ). My non-thinking activities, however, are insufficient. For instance, it's no good to reason that “I exist, since I am walking,” because methodic doubt calls into question the existence of my legs. Maybe I'm just dreaming that I have legs. A simple revision, such as “I exist since it seems I'm walking,” restores the anti-sceptical potency (cf. Replies 5, AT ; Prin. ).

Fourth, a caveat is in order. That Descartes rejects formulations presupposing the existence of a body commits him to no more than an epistemic distinction between the ideas of mind and body, but not yet an ontological distinction (as in so-called mind-body dualism). Indeed, in the passage following the cogito, Descartes has his meditator say:

And yet may it not perhaps be the case that these very things which I am supposing to be nothing [e.g., “that structure of limbs which is called a human body”], because they are unknown to me, are in reality identical with the “I” of which I am aware? I do not know, and for the moment I shall not argue the point, since I can make judgements only about things which are known to me. (Med. 2, AT )

In short, the success of the cogito does not presuppose Descartes' mind-body dualism.

Fifth, much of the debate over whether the cogito involves inference, or is instead a simple intuition (roughly, self-evident), is preempted by two observations. One observation concerns the absence of an express ‘ergo’ (‘therefore’) in the Second Meditation account. It seems a mistake to emphasize this absence, as if suggesting that Descartes denies any role for inference. For the Second Meditation passage is the one place (of his various published treatments ) where Descartes explicitly details a line of inferential reflection leading up to the conclusion that I am, I exist. His other treatments merely say the ‘therefore’; the Meditations treatment unpacks it. A second observation is that it seems a mistake to assume that the cogito must either involve inference, or intuition, but not both. There is no inconsistency in claiming a self-evident grasp of a proposition with inferential structure. It is indeed widely held among philosophers today that modus ponens is self-evident, yet it contains an inference. In short, that a statement contains an inference does not entail that our acceptance of it is grounded in inference — a fact applicable to the cogito. As Descartes writes:

When someone says “I am thinking, therefore I am, or I exist,” he does not deduce existence from thought by means of a syllogism, but recognizes it as something self-evident by a simple intuition of the mind. (Replies 2, AT )

Whatever the cogito's inferential status, it is worth noting a twofold observation of Barry Stroud: “a thinker obviously could never be wrong in thinking ‘I think’”; moreover, “no one who thinks could think falsely that he exists” (, ).

Finally, Descartes' reference to an “I”, in the “I think”, is not intended to presuppose the existence of a substantial self. In the very next sentence following the initial statement of the cogito, the meditator says: “But I do not yet have a sufficient understanding of what this ‘I’ is, that now necessarily exists” (Med. 2, AT ). The cogito purports to yield certainty that I exist insofar as I am a thinking thing, whatever that turns out to be. The ensuing discussion is intended to help arrive at an understanding of the ontological nature of the thinking subject.

More generally, we should distinguish issues of epistemic and ontological dependence. In the final analysis, Descartes thinks he shows that the occurrence of thought depends (ontologically) on the existence of a substantial self — to wit, on the existence of an infinite substance, namely God (cf. Med. 3, AT ff). But Descartes denies that an acceptance of these ontological matters is epistemically prior to the cogito: its certainty is not supposed to depend (epistemically) on the abstruse metaphysics that Descartes thinks he eventually establishes.

If the cogito does not presuppose a substantial self, what then is the epistemic basis for injecting the “I” into the “I think”? Some critics have complained that, in referring to the “I”, Descartes begs the question by presupposing what he means to establish in the “I exist.” Among the critics, Bertrand Russell objects that “the word ‘I’ is really illegitimate.” Echoing the 18th century thinker, Georg Lichtenberg, Russell writes that Descartes should have, instead, stated “his ultimate premiss in the form ‘there are thoughts’.” Russell adds that “the word ‘I’ is grammatically convenient, but does not describe a datum.” (, ) Accordingly, “there is pain” and “I am in pain” have different contents, and Descartes is entitled only to the former.

One effort at reply has it that introspection reveals more than what Russell allows — it reveals the subjective character of experience. On this view, there is more to the experiential story of being in pain than is expressed by saying that there is pain: the experience includes the feeling of pain plus a point-of-view — an experiential addition that's difficult to characterize except by adding that “I” am in pain, that the pain is mine. Importantly, my awareness of this subjective feature of experience does not depend on an awareness of the metaphysical nature of a thinking subject. If we take Descartes to be using ‘I’ to signify this subjective character, then he is not smuggling in something that's not already there: the “I”-ness of consciousness turns out to be (contra Russell) a primary datum of experience. Though, as Hume persuasively argues, introspection reveals no sense impressions suited to the role of a thinking subject, Descartes, unlike Hume, has no need to derive all our ideas from sense impressions. Descartes' idea of the self does ultimately draw on innate conceptual resources.

But how could ideas deriving from the subjective character of experience justify a substantive metaphysical conclusion about the existence of a real self? On one plausible line of reply, Descartes does not yet intend to be establishing the metaphysical result; rather, the initial intended result is merely epistemic. Early in the Third Meditation, Descartes says that the epistemic basis of the cogito is, at this juncture, simply that it is clearly and distinctly perceived. Yet the truth of what is clearly and distinctly perceived has yet to be established. The cogito initially establishes merely that we cannot but assent to our existence; the stronger, metaphysical result is established only upon demonstrating the veracity of clear and distinct perception. This line of interpretation does, of course, imply that the cogito does not initially count as full-fledged Knowledge — an issue to which we now turn.

### But is it Knowledge?

There are interpretive disputes about whether the cogito is supposed to count as indefeasible Knowledge. (That is, about whether it thus counts upon its initial introduction, prior to the arguments for God.) Many commentators hold that it is supposed to count, but the case for this interpretation is by no means clear.

There is no disputing that Descartes characterizes the cogito as the “first item of knowledge [cognitione]” (Med. 3, AT ); as the first “piece of knowledge [cognitio]” (Prin. , AT 8a:7). Noteworthy, however, is the Latin terminology (‘cognitio’ and its cognates) that Descartes uses in these characterizations. As discussed in Section , Descartes is a contextualist in the sense that he uses ‘knowledge’ language in two different contexts of clear and distinct judgments: the less rigorous context includes defeasible judgments, as in the case of the atheist geometer (who can't block hyperbolic doubt); the more rigorous context requires indefeasible judgments, as with the brand of Knowledge sought after in the Meditations.

Worthy of attention is that Descartes characterizes the cogito using the same cognitive language that he uses to characterize the atheist's defeasible cognition. Recall that Descartes writes of the atheist's clear and distinct grasp of geometry: “I maintain that this awareness [cognitionem] of his is not true knowledge [scientiam]” (Replies 2, AT ). This alone does not prove that the cogito is supposed to be defeasible. It does, however, prove that calling it the “first item of knowledge [cognitione]” doesn't entail that Descartes intends it as indefeasible Knowledge.

Bearing further on whether the cogito counts as indefeasible Knowledge — prior to having refuted the Evil Genius Doubt — is the No Atheistic Knowledge Thesis (cf. Section above). Descartes makes repeated and unequivocal statements implying this thesis. Consider the following texts, each arising in a context of clarifying the requirements of indefeasible Knowledge (all italics are mine):

For if I do not know this [i.e., “whether there is a God, and, if there is, whether he can be a deceiver”], it seems that I can never be quite certain about anything else. (Med. 3, AT )

I see that the certainty of all other things depends on this [knowledge of God], so that without it nothing can ever be perfectly known [perfecte sciri]. (Med. 5, AT )

[I]f I did not possess knowledge of God … I should thus never have true and certain knowledge [scientiam] about anything, but only shifting and changeable opinions. (Med. 5, AT )

And upon claiming finally to have achieved indefeasible Knowledge:

Thus I see plainly that the certainty and truth of all knowledge [scientiae] depends uniquely on my awareness of the true God, to such an extent that I was incapable of perfect knowledge [perfecte scire] about anything else until I became aware of him. (Med. 5, AT )

These texts make a powerful case that nothing else can be indefeasibly Known prior to establishing that we're creatures of an all-perfect God, rather than an evil genius. These texts make no exceptions. Descartes looks to hold that hyperbolic doubt is utterly unbounded — that it undermines all manner of propositions, including therefore the proposition that “I exist.”

By contrast, other texts seem to support the interpretation whereby the cogito counts as indefeasible Knowledge. For example, we have seen texts making clear that it resists hyperbolic doubt. Often overlooked, however, is that it is only subsequent to the introduction of the cogito that Descartes has his meditator first notice the manner in which clear and distinct perception is both resistant and vulnerable to hyperbolic doubt: the extraordinary certainty of such perception resists hyperbolic doubt while it is occurring; it is vulnerable to hyperbolic doubt upon redirecting one's perceptual attention away from the matter in question. This theme is developed more fully in the next Section.

As will emerge, there are two main kinds of interpretive camps concerning how to deal with the so-called Cartesian Circle. The one camp contends that hyperbolic doubt is utterly unbounded. On this view, the No Atheist Knowledge Thesis is taken quite literally. The other camp contends that hyperbolic doubt is bounded; that is, that the cogito, and a few other special truths, are in a lockbox of sorts, utterly protected from even the most hyperbolic doubt. This view allows that atheists can have indefeasible Knowledge. These two kinds of interpretations are developed in Section 6.

Further reading: For important passages in Descartes' handling of the cogito, see the second and third sets of Objections and Replies. In the secondary literature, see Beyssade (), Broughton (), Carriero (), Cunning (), Curley (), Frankfurt (), Hintikka (), Kenny (), Markie (), Peacocke (), Sarkar (), Stroud (), Vendler (), Vinci (), Williams (), and Wilson ().

## 5. Epistemic Privilege and Defeasibility

The extraordinary certainty and doubt-resistance of the cogito marks an Archimedean turning point in the meditator's inquiry. Descartes builds on its impressiveness to help clarify further epistemic theses. The present Section considers two such theses about our epistemically privileged perceptions. First, that clarity and distinctness are, jointly, the mark of our epistemically best perceptions (notwithstanding that such perception remains defeasible). Second, that judgments about one's own mind are epistemically privileged compared with those about bodies.

### Our Epistemic Best: Clear and Distinct Perception and its Defeasibility

The opening four paragraphs of the Third Meditation are pivotal. Descartes uses them to characterize our epistemically best perceptions, while clarifying also that even this impressive epistemic ground falls short of the goal of indefeasible Knowledge. This sobering realization leads to Descartes' infamous efforts to refute the Evil Genius Doubt, by proving an all-pefect (and therefore non-deceiving) God.

The first and second paragraphs portray the meditator attempting to build on the success of the cogito by identifying a general principle of certainty: “I am certain that I am a thinking thing. Do I not therefore also know what is required for my being certain about anything?” (AT ). What are the phenomenal marks of this impressive perception — what is it like to have perception that good? Descartes' answer: “In this first item of knowledge [cognitione] there is simply a clear and distinct perception of what I am asserting” (ibid.).

The third and fourth paragraphs help clarify (among other things) what Descartes takes to be epistemically impressive about clear and distinct perception, though absent from external sense perception. The third paragraph has the meditator observing:

Yet I previously accepted as wholly certain and evident many things which I afterwards realized were doubtful. What were these? The earth, sky, stars, and everything else that I apprehended with the senses. But what was it about them that I perceived clearly? Just that the ideas, or thoughts, of such things appeared before my mind. Yet even now I am not denying that these ideas occur within me. But there was something else which I used to assert, and which through habitual belief I thought I perceived clearly, although I did not in fact do so. This was that there were things outside me which were the sources of my ideas and which resembled them in all respects. Here was my mistake; or at any rate, if my judgement was true, it was not thanks to the strength of my perception. (Med. 3, AT )

The very next paragraph (the fourth) draws an epistemically important contrast with external sense perception (as just characterized). External sense perception does not admit of any great “strength of perception,” quite unlike clear and distinct perception. As earlier noted (Section ), the certainty of interest to Descartes is psychological in character, though not merely psychological. Not only does occurrent clear and distinct perception resist doubt, it provides a kind of cognitive illumination. Both of these epistemic virtues — its doubt-resistance, and its luminance — are noted in the fourth paragraph:

[Regarding] those matters which I think I see utterly clearly with my mind's eye … when I turn to the things themselves which I think I perceive very clearly, I am so convinced by them that I spontaneously declare: let whoever can do so deceive me, he will never bring it about that I am nothing, so long as I continue to think I am something; or make it true at some future time that I have never existed, since it is now true that I exist; or bring it about that two and three added together are more or less than five, or anything of this kind in which I see a manifest contradiction. (Med. 3, AT )

The contrast drawn in the third and fourth paragraphs gets at a theme that Descartes thinks crucial to his broader project: namely, that there is “a big difference” — an introspectible difference — between external sense perception, and perception that is genuinely clear and distinct. The external senses result in, at best, “a spontaneous impulse” to believe something — an impulse we're able to resist, even while it occurs. By contrast, clear and distinct perception is utterly irresistible while occurring: “Whatever is revealed to me by the natural light — for example that from the fact that I am doubting it follows that I exist, and so on — cannot in any way be open to doubt.” (Med. 3, AT ) As Descartes repeatedly conveys: “my nature is such that so long as I perceive something very clearly and distinctly I cannot but believe it to be true” (Med. 5, AT ; cf. , , , 8a:9).

Because of the epistemic impressiveness of clear and distinct perception (notably, as exhibited in the cogito), the meditator concludes that such perception will issue as the mark of truth, if anything will. He tentatively formulates the following candidate for a criterion of truth: “I now seem [videor] to be able to lay it down as a general rule that whatever I perceive very clearly and distinctly is true” (Med. 3, AT ). Let us call this general principle the ‘C&D Rule’. The announcement of the candidate criterion is carefully tinged with caution (videor), as the C&D Rule has yet to be subjected to hyperbolic doubt. Should it turn out that clarity and distinctness — as an epistemic ground — is shakable, then, there would remain some doubt about the general veracity of clear and distinct perception. In that case, when reflecting back on having perceived something clearly and distinctly, it would not seem so impressive, after all — it “would not be enough to make me certain of the truth of the matter” (ibid.). This cautionary note anticipates the sobering realization of the fourth paragraph, that, for all its impressiveness, even clear and distinct perception is in some sense defeasible, at this stage of the inquiry.

In what sense defeasible? Recall that the Evil Genius Doubt is, fundamentally, a doubt about our cognitive natures. Maybe my mind was made flawed, such that I go wrong even when my perception is clear and distinct. As the meditator conveys in the fourth paragraph, my creator might have “given me a nature such that I was deceived even in matters which seemed most evident,” with the consequence that “I go wrong even in those matters which I think I see utterly clearly with my mind's eye” (AT ). The result is a kind of epistemic schizophrenia:

Moments of epistemic optimism: While I am directly attending to a proposition — perceiving it clearly and distinctly — I enjoy an irresistible cognitive luminance and my assent is compelled.

Moments of epistemic pessimism: When no longer directly attending — no longer perceiving the proposition clearly and distinctly — I can entertain the sceptical hypothesis that such feelings of cognitive luminance are epistemically worthless, arising from a defective cognitive nature.

The doubt is thus indirect, in the sense that these moments of epistemic pessimism arise when I am no longer directly attending to the propositions in question. This indirect operation of hyperbolic doubt is conveyed not only in the fourth paragraph, but in numerous other texts, including the following:

Admittedly my nature is such that so long as I perceive something very clearly and distinctly I cannot but believe it to be true. But my nature is also such that I cannot fix my mental vision continually on the same thing, so as to keep perceiving it clearly; and often the memory of a previously made judgement may come back, when I am no longer attending to the arguments which led me to make it. And so other arguments can now occur to me which might easily undermine my opinion, if I were unaware of [the true] God; and I should thus never have true and certain knowledge about anything, but only shifting and changeable opinions. For example, when I consider the nature of a triangle, it appears most evident to me, steeped as I am in the principles of geometry, that its three angles are equal to two right angles; and so long as I attend to the proof, I cannot but believe this to be true. But as soon as I turn my mind's eye away from the proof, then in spite of still remembering that I perceived it very clearly, I can easily fall into doubt about its truth, if I am unaware of God. For I can convince myself that I have a natural disposition to go wrong from time to time in matters which I think I perceive as evidently as can be. (Med. 5, AT –70; cf. AT –65; AT 8a:9–10).

Granted, this indirect doubt is exceedingly hyperbolic. Even so, it means that we lack fully indefeasible Knowledge. Descartes thus closes the fourth paragraph as follows:

And since I have no cause to think that there is a deceiving God, and I do not yet even know for sure whether there is a God at all, any reason for doubt which depends simply on this supposition is a very slight and, so to speak, metaphysical one. But in order to remove even this slight reason for doubt, as soon as the opportunity arises I must examine whether there is a God, and, if there is, whether he can be a deceiver. For if I do not know this, it seems that I can never be quite certain about anything else. (Med. 3, AT )

The leading role played by the cogito in this four paragraph passage is easily overlooked. Not only is it (in paragraph two) the exemplar of judging clearly and distinctly, it is listed (paragraph four) among the propositions that are compellingly certain while attended to, though undermined when we no longer thus attend. The implication is that cogito, like 2+3=5, is something to which we cannot but assent while attending clearly and distinctly, but which we can later doubt in moments of epistemic pessimism, when no longer attending clearly and distinctly.

What next? How does Descartes think we're to make epistemic progress if even our epistemic best is subject to hyperbolic doubt? This juncture of the Third Meditation (the end of the fourth paragraph) marks the beginning point of Descartes' notorious efforts to refute the Evil Genius Doubt. His efforts involve an attempt to establish that we are the creatures not of an evil genius, but an all-perfect creator who would not allow us to be deceived about what we clearly and distinctly perceive. Before turning our attention (in Section 6) to these efforts, let's digress somewhat to consider a Cartesian doctrine that has received much attention in its subsequent history.

### The Epistemic Privilege of Judgments About the Mind

Descartes holds that our judgments about our own minds are epistemically better-off than our judgments about bodies. In our natural, pre-reflective condition, however, we're apt to confuse the sensory images of bodies with the external things themselves, a confusion leading us to think our judgments about bodies are epistemically impressive. The confusion is clearly expressed (Descartes would say) in G. E. Moore's famous claim to knowledge — “Here is a hand” — along with his more general defense of common sense:

I begin, then, with my list of truisms, every one of which (in my own opinion) I know, with certainty, to be true. … There exists at present a living human body, which is my body. This body was born at a certain time in the past, and has existed continuously ever since … But the earth had existed also for many years before my body was born … (, 32–33)

In contrast, Descartes writes:

[I]f I judge that the earth exists from the fact that I touch it or see it, this very fact undoubtedly gives even greater support for the judgement that my mind exists. For it may perhaps be the case that I judge that I am touching the earth even though the earth does not exist at all; but it cannot be that, when I make this judgement, my mind which is making the judgement does not exist. (Prin. , AT 8a:8–9)

Methodical doubt is intended to help us appreciate the folly of the commonsensical position — helping us to recognize that the perception of our own minds is “not simply prior to and more certain … but also more evident” than that of our own bodies (Prin. , AT 8a:8). “Disagreement on this point,” writes Descartes, comes from “those who have not done their philosophizing in an orderly way”; from those who, while properly acknowledging the “certainty of their own existence,” mistakenly “take ‘themselves’ to mean only their bodies” — failing to “realize that they should have taken ‘themselves’ in this context to mean their minds alone” (Prin. , AT 8a:9).

In epistemological contexts, Descartes underwrites the mind-better-known-than-body doctrine with methodic doubt. For example, while reflecting on his epistemic position in regards both to himself, and to the wax, the Second Meditation meditator says:

Surely my awareness of my own self is not merely much truer and more certain than my awareness of the wax, but also much more distinct and evident. For if I judge that the wax exists from the fact that I see it, clearly this same fact entails much more evidently that I myself also exist. It is possible that what I see is not really the wax; it is possible that I do not even have eyes with which to see anything. But when I see, or think I see (I am not here distinguishing the two), it is simply not possible that I who am now thinking am not something. (Med. 2, AT )

Other reasons may motivate Descartes as well. For the doctrine may be closely allied to a representational theory of sense perception. Accordingly, our sense organs and nerves serve as literal mediating links in the perceptual chain: they stand between (both spatially and causally) external things themselves, and the brain events that occasion our perceptual awareness (cf. Prin. ). In veridical sensation, the objects of immediate sensory awareness are not external bodies themselves, nor are we immediately aware of the states of our sense organs or nerves. Rather, the objects of immediate awareness are — whether in veridical sensation, or in dreams — the mind's own ideas. Descartes indeed holds that the fact of physiological mediation helps explain delusional ideas, because roughly the same kinds of physiological processes that produce waking ideas are employed in producing delusional ideas:

[I]t is the soul which sees, and not the eye; and it does not see directly, but only by means of the brain. That is why madmen and those who are asleep often see, or think they see, various objects which are nevertheless not before their eyes: namely, certain vapours disturb their brain and arrange those of its parts normally engaged in vision exactly as they would be if these objects were present. (Optics, AT ; cf. Med. 6, AT ff; Passions 26)

Various passages of the Meditations lay important groundwork for this theory of perception. For instance, one of the messages of the wax passage is that sensory awareness does not reach to external things themselves:

We say that we see the wax itself, if it is there before us, not that we judge it to be there from its colour or shape; and this might lead me to conclude without more ado that knowledge of the wax comes from what the eye sees, and not from the scrutiny of the mind alone. But then if I look out of the window and see men crossing the square, as I just happen to have done, I normally say that I see the men themselves, just as I say that I see the wax. Yet do I see any more than hats and coats which could conceal automatons? I judge that they are men. (Med. 2, AT )

Descartes thinks we're apt to be “tricked by ordinary ways of talking” (ibid.). In ordinary contexts we don't say that it seems there are men outside the window; we say we see them. Nor, in such contexts, are our beliefs about those men apt to result from conscious, inferentially complex judgments, say, like this one: “Well, I appear to be awake, and the window pane looks clean, and there's plenty of light outside, and so on, and I thus conclude that I am seeing men outside the window.” Even so, our ordinary ways of speaking and thinking often mislead. Descartes' view is that the mind's immediate perception does not, strictly speaking, extend beyond itself, to external bodies. This is an important basis of the mind-better-known-than-body doctrine. In the concluding paragraph of the Second Meditation, Descartes writes:

I see that without any effort I have now finally got back to where I wanted. I now know that even bodies are not strictly [proprie] perceived by the senses or the faculty of imagination but by the intellect alone, and that this perception derives not from their being touched or seen but from their being understood; and in view of this I know plainly that I can achieve an easier and more evident perception of my own mind than of anything else. (Med. 2, AT )

Related is a Third Meditation remark. Discussing sense perception and our ideas of external things, Descartes writes that the mind's sensation extends strictly and immediately only to the ideas: “the ideas were, strictly speaking, the only immediate objects of my sensory awareness [solas proprie et immediate sentiebam]” (Med. 3, AT ). The theme that ideas are the only immediate objects of awareness repeats itself elsewhere in Descartes' writings. As he tells Hobbes: “I make it quite clear in several places … that I am taking the word ‘idea’ to refer to whatever is immediately perceived by the mind” (Replies 3, AT ).

Complicating an understanding of such passages is that Descartes scholarship is divided on whether to attribute to him some version of an indirect theory of perception, or instead some version of a direct theory. According to indirect perception accounts, in normal sensation the mind's perception of bodies is mediated by an awareness of its ideas of those bodies. By contrast, direct perception interpretations allow that in normal sensation the mind's ideas play a mediating role, though this role doesn't have ideas functioning as items of awareness; rather, the objects of direct awareness are the external things, themselves. On both accounts, ideas mediate our perception of external objects. On direct theory accounts, the mediating role is only a process role. By analogy, various brain processes mediate our perception of external objects, but in the normal course of perception we are not consciously aware of those processes; and likewise for the mind's ideas, according to direct perception accounts. On one recent version of an indirect perception interpretation, sensory ideas mediate our perception of the external bodies they're of, in much the same way that pictures (or other representational media) mediate our perception of what they portray (Newman ). More generally, Descartes seems to view all ideas as mental pictures, of a sort. As he writes: “the term ‘idea’ is strictly appropriate” only for thoughts that “are as it were the images of things” (Med. 3, AT ); he adds that “the ideas in me are like {pictures, or} images” (Med. 3, AT ).