Descartes & the Cogito

DESCARTES’ CURE (PART 1): THE COGITO & THE (ALLEGED) DEMISE OF BROAD KNOWLEDGE SKEPTICISM

Si fallor, sum (“If I am mistaken, I exist”) — Augustine of Hippo, De Civitate Dei XI,26

Now someone who sees perceives that he sees; one who hears perceives that he hears; one who walks perceives that he walks; and similarly in the other human cases also there is some [faculty] that perceives that we are active; so that if we are perceiving, we perceive that we are perceiving, and if we are thinking, we perceive that we are thinking. Now perceiving that we are perceiving or thinking is the same as perceiving that we [exist]…. — Aristotle, Nicomachean Ethics 1170a30 [This] truth ‘I am thinking, therefore I exist’ [is] so solid and secure that the most extravagant suppositions of the skeptics could not overthrow it. — Descartes, Discourse on Method

[B]y not positively affirming that they are [exist], the skeptics ward off the appearance of error in themselves, yet they do make errors simply by showing [they exist]; one cannot err who is not [real]. That we [exist] is therefore not only true, but it is altogether certain as well. — Augustine of Hippo, Enchiridion 7,xx

Descartes’ post-First Meditation epistemic status THE BIG IDEAS TO MASTER Though Descartes’ post-First Meditation epistemic status is • The transparency of the mental thesis such that it looks like nothing can satisfy the criteria for being • The incorrigibility of belief thesis a member of the set of foundational beliefs (that is, it looks • The indefeasibility of belief thesis like there are no certain and indubitable propositions), he • The cogito as an argument vs. the cogito as a performative considers a particular claim to determine whether it is a “demon-proof point of certainty.” This claim is his famous claim: cogito ergo sum (hereafter, the cogito). What does the cogito say? Simply this: I think, therefore I am.1 And this he believes will save science from the broad knowledge skeptics. For it is the “one firm and immovable [Archimedean] point” that he seeks to find to establish a new foundation for science. With that said, we can say that:

The purposes of the cogito

§ To show that the propositions ‘I think’ and ‘I exist’ are certain and indubitable, and § To provide one key part of the epistemic foundation for all propositional knowledge and epistemically warranted belief. It is on these two slender bases that he will begin to establish the correct use of our faculties, and build the new science. Of course, this requires both that the cogito is certain and indubitable, and it is from that he can build a new science. Is he correct about these?

Descartes’ argument for the certainty and indubitability of the cogito According to Descartes, the demon doubt cannot undermine the claims I am thinking and I exist. This is for three reasons:

1 If you pay careful attention, you will note that the expression ‘I think therefore I am’ is never stated in his Meditations on First Philosophy. That version of the expression actually comes from his Discourse on Method of Rightly Conducting the Reason, and Seeking Truth in the Sciences (1637) and his Principles of Philosophy (1644). 1. The word ‘deceived’ means led to think things that are false. So, if S is being deceived, then S is led to think things that are false. What’s more, if S is thinking things that are false, then S is thinking. 2. It is not possible that I mistakenly think that I am thinking given that that is itself thinking. 3. If the demon is deceiving me, then I must exist to be deceived.

The skeletal skeptical argument used To see this, first consider the evil demon skeptical argument with respect to the proposition I am thinking. Using The Skeletal Skeptical Argument, if we replace ‘p’ with I am thinking and ‘sk’ with There is an evil demon deceiving me into believing that p, we get the following argument: i. I know that I am thinking only if I know that there is not an evil demon deceiving me into believing that I am thinking. ii. I know that there is not an evil demon deceiving me into believing that I’m thinking only if I can rule out that there is an evil demon deceiving me into believing that I am thinking iii. It’s not the case that I can rule out that there is not an evil demon deceiving me into believing that I am thinking. Therefore, iv. I do not know that I am thinking.

Descartes’ attack on (iii) Says Descartes, the argument is valid but unsound. He rejects (iii) given that he thinks (iii) is necessarily false. That is, he believes that there is no possible way for the following to be true:

SG: One is made to think she is thinking, and not be thinking, whether by deception or not. Consider the following intuitive proof that that is so:

A. If, at some time t, a person S1 deceives a person S2 that a proposition p is true, then S2 is thinking at t (that p is true).

B. If S2 is thinking at some time t (that p is true), then it is impossible that S2 also believe S2 is thinking at t is and that belief be false. Therefore,

C. If, at some time t, a person S1 deceives a person S2 that a proposition p is true, then it is impossible that S2

also believe S2 is thinking at t is and that belief be false.

Three important presuppositions in Descartes’ Meditations It is clear that Descartes has presupposed three very important principles in his discussion. These are important to be aware of not only so that we better understand his positions, but that the three principles may be open to attack. The three principles are as follows: Presupposition 1 – The Transparency of the Mental Thesis The transparency of the mental thesis is an important claim about the nature and being in any (possible) mental state. That is, it tells us what must be true if we are to be in a mental state. What is that thesis? It says that

TRANSPARENCY: If a person S is in a mental state s, then S is aware of being in s.

As we can see, TRANSPARENCY tells us that there’s an important relationship between being in certain mental state and a person’s awareness of that state. According to the thesis, if a person is not aware of being in a mental state s, then he cannot be in s, for instance, if Jones is not aware of being in pain, then Jones cannot be in pain. Alternatively, whenever Jones is in pain, then Jones will be aware of being in pain.

Presupposition 2 – The Incorrigibility of a Belief Thesis The incorrigibility of a belief thesis is an important claim about the nature of a certain class of beliefs, namely, beliefs about the appearances. What is that thesis? It says that

INCORRIGIBILITY: If a person S believes that x appears F, then S cannot be corrected that x appears F.

It should be clear that INCORRIGIBILITY has to do with the possibility of being corrected about how things appear. According to the thesis, a person cannot be corrected about how things appear to her. For instance, if Smith believes that the object before appears to be black, then in fact the object does actually appear to be black. That doesn’t imply the object is black. No, Smith might be looking at a yellow lemon in green light. In such conditions, yellow objects such as lemons are presented to (at least) human perceivers as black. Even so, there’s nothing that could overturn the fact that lemon appears to Smith to be black.

Presupposition 3 – The Indefeasibility of a Belief Thesis The indefeasibility of a belief thesis is another important claim about a certain class of beliefs. However, it’s importantly different from INCORRIGIBILITY. It doesn’t tell us about appearance beliefs, but rather about the possibility of certain beliefs going from epistemic warranted to epistemically unwarranted. What is the thesis? It says that

INDEFEASIBILITY: S’s belief that p is indefeasible if there is no new evidence e that could (in principle) overturn S’s being epistemically warranted in believing that p.

Notice that INDEFEASIBILITY doesn’t say anything about the possibility of being corrected about a certain belief; it tells us that a belief is indefeasible if a person’s having the belief will always be epistemically warranted. For instance, if Brown believes the proposition all red things are red, then Brown’s belief is indefeasible if it’s in principle impossible for there to be any evidence that renders Brown’s belief epistemically unwarranted.

Without TRANSPARENCY, INCORRIGIBILITY, and INDEFEASIBILITY, Descartes could not make his Cogito case work. Why? According to Descartes, a person S’s thinking that I’m thinking and I exist are such that:

a) S can’t be in those states and fail to be aware of being in those states (TRANSPARENCY), b) S can’t be corrected whether or not it appears that S is in those states (INCORRIGIBILITY), and c) There’s no possible evidence that could undermine S’s epistemic warrant in believing that S is thinking and S exists (INDEFEASIBILITY).

Are they true, or is there reason to reject one or more of these claims?2