IV. Cartesian Foundationalism

      A. Descartes and the Meditations

René Descartes (1596-1650)
- French philosopher and mathematician.
- Invented Analytic Geometry and the Cartesian System of Coordinates
- Greatest Philosophical Work: Meditations on First Philosophy (1641)
- Called "the father of modern philosophy"
- Said "Cogito Ergo Sum."

      B. Descartes Project: Foundationalism

Foundationalism is a type of theory of epistemic justification.  Sober writes:

"The word foundationalism should make you think of a building.  What keeps a building from falling over?  The answer has two parts.  First, there is a solid foundation.  Second, the rest of the building, which I'll call the superstructure, is attached securely to that foundation" (158).

Although Sober never states foundationalism explicitly, I will: 


S is justified in believing that p if and only if either

(i) p is entailed by beliefs that are themselves justified for S; or
(ii) p is self-justifying for S.

To relate Sober's analogy to this theory: clause (ii) corresponds to the foundation of the building; clause (i) corresponds to the superstructure; the idea of the superstructure being "attached securely" to the foundation is captured with the concept of entailment.

Different ways of spelling out what 'self-justifying' means will yield different versions of Foundationalism.  Descartes seems to endorse the following rather stringent account of self-justification:

p is self-justifying for S iff p is indubitable for S.

This yields Cartesian Foundationalism (CF):

CF: S is epistemically justified in believing p if and only if either

(i) p is entailed by beliefs that are themselves justified for S; or
(ii) p is indubitable for S.

      C. Descartes Method: Doubt

            1. Indubitability

All that's left in order to understand CF is to explain what 'indubitable' means.  Here is what it means:

p is indubitable for S if and only if necessarily, if S believes p, then p is true.

This is a very strange property.  For a proposition to have this property for you, it means that the very act of your believing it guarantees that it is true.  This property seems so strange because why should the mere act of believing something ensure that it is true?

To prove that some belief of his is not indubitable, Descartes will try to doubt it.  To do this he will try to imagine a scenario in which things are just as they currently seem to Descartes, but in which the belief is false.  This will show that the very act of his believing the proposition does not guarantee that it is true.

            2. Tools to Prove Dubitability

Descartes finds that it is not easy to doubt certain beliefs, such as, for instance, the belief that he has hands.  So he uses the following tools to help him doubt what seems obvious to him.

                  a. The Dream Argument
                  b. The Evil Genius Hypothesis

In class, we mentioned four competing hypotheses about the way the world is.  These are as follows, with one more I just added:

- The Common Sense Hypothesis
- The Truman Show Hypothesis
- The Matrix Hypothesis
- The Brain-in-a-Vat Hypothesis
- The Evil Genius Hypothesis

(The Brain-in-a-Vat Hypothesis is a lot like the Matrix hypothesis, except that in the Brain-in-a-Vat Hypothesis, you don't even have a body.  You are just a brain floating in a vat with electrodes stuck into you, feeding you false experiences about the world.)

Each hypothesis is more radical than the next.  But each hypothesis is consistent with how things seem to us.  Therefore, apparently we have not a shred of evidence that favors the Common Sense Hypothesis over any of the others.

Descartes doesn't actually believe that the Evil Genius Hypothesis is true.  He just pretends that it is whenever he finds himself believing things that not indubitable.  He uses it as a sort of antidote to our common tendency to believe what is less than certain.

      D. The Cogito

Descartes finds that the following proposition is indubitable: I exist.  He sees that he can be certain that he exists, because even if there is an evil genius doing everything it can to deceive Descartes, it can't deceive him into believing he doesn't exist.  In order for something to be deceived, it must at least exist.  Every time a being has the thought that it exists, that belief must be true, even if the being is deceived about everything else.

Descartes is right about this.  The very act of Descartes believing "I exist" guarantees that it is true, because the act of believing requires there to be a thing doing the believing.

      E. The Primacy of the Mental

            1. Incorrigibility

Descartes also thinks that he can be absolutely certain about the contents of his mind, such as his sensations, thoughts, feelings, and desires.  For example, he thinks the proposition "I have a headache" is indubitable for him.  So long as you think you have a headache, then you have one, according to Descartes.  Sober (163-4) describes reasons why some people are reluctant to agree with Descartes that we have perfect knowledge about all of our mental states.

            2. Personal Identity

Another way in which Descartes emphasizes the mental is in answering the question, What am I?  In Meditation II, Descartes concludes that he is his mind -- i.e., that he is a thinking thing.  The implication is that he is not his body -- i.e., he is not a physical object.  He is not his body, he says, because he's not even sure his body exists. Since he is sure that he exists, he must not be his body.  Since he is certain that he exists, and he is certain only that he has a mind, he concludes that he must just be his mind.

What do you think about this argument?


      F. Building the Superstructure

Descartes is emphatically not a skeptic.  He believes we can have knowledge.  So he needs to show a way that he can know (i.e., be absolutely certain that) he's not being fooled by an evil genius, that the external world really exists and is not just a hallucination.

His current set of foundational beliefs consists of the belief that he exists along with all his beliefs about his own mental states.  Is this current foundation enough to build up knowledge about the external world?  No. There is a "gap" between the contents of our mind and the external world.  Just because it appears to us that there is a physical world out there with certain features, it does not follow that there really is one.  Maybe you can be certain that it seems to you that, for example, you have hands, or that there is a table in front of you.  But nothing about the external world follows from the fact that things seem this way to you.

            1. Cosmological Argument for the Existence of God

Descartes then attempts to get another belief into the foundation: the belief that God exists.  To do this, Descartes must show that it is indubitable.  See Sober (166-8) for the argument.

Descartes also tries to get this belief into the foundation: that God is no deceiver.

            2. Descartes' Truth Rule: Clarity and Distinctness

Then Descartes comes up with a crucial rule, a rule which enables him to erect the building of knowledge much higher.  Sober calls is the "Clarity and Distinctness Criterion."  It says this:

"Whatever I clearly and distinctly perceive to be true is true."

So descartes thinks that, so long as he is really careful, and doesn't form beliefs unless they are clear and distinct, he won't make any epistemic mistakes.  This is supposed to follow from the fact that God is not a deceiver.

            3. A Cartesian Circle?

Many commentators accuse Descartes of arguing in a circle here.  They think that Descartes used this Clarity and Distinctness Criterion to prove that God is no deceiver.  And then that he used the claim that God is no deceiver to prove the Clarity and Distinctness Criterion.  This has come to be called the Cartesian Circle.  There is controversy among scholars, however, about whether Descartes is in fact arguing in a circle here.


      G. Skepticism Avoided?

Here is how Descartes avoids skepticism.  He bridges the gap between the mere appearance of an external world and knowledge of an external world by allegedly proving that all his clear and distinct perceptions are true.  So if he is being really careful, and waits until he has a clear and distinct perception that the external world exists, he can be absolutely certain that this belief is true.

Convinced?  Me neither?