Cartesian MeditationsFrom the Destruction of our Beliefs to the Beginnings of Certainty

René Magritte, “The Human Condition”

1 Background

According to Descartes, the right way to make progress in any Science is to:

1) Accept only what is so clear in one's own mind as to exclude any doubt,

2) split large difficulties into smaller ones,

3) argue from the simple to the complex, and

4) check, when one is done.This is the overall structure of the Meditations.

2 Background

Descartes is looking for a firm foundation for the sciences.

His opponents are empiricists. They believe that knowledge must come from originally from the senses. Descartes believes that most people naively believe that empiricism is true.

Descartes, just like the empiricists, accepts foundationalism.

Foundationalism is the view that all knowledge must rest on certain privileged basic beliefs. These beliefs are then able to provide justification for all the other beliefs a person has.

But how do we get to the roots of our beliefs?

And can we demolish them to rebuild them anew?

And, thinking about it, are we sure our beliefs have roots at all?

Two Challenges to the Method of Doubt

Challenge I: Our beliefs may not be structured like a logical tree, based on some small set of basic beliefs. Rather, as coherentism argues, our beliefs may form an a web of beliefs whose justifications are interdependent. Some may be more central than others, but none are absolutely basic as the foundationalist claims.

Challenge II: Hume argues that we cannot subject all of our beliefs to doubt in this way because we must always rely on most of them being true in order to act

Belief Change in Action:

The Ship of Theseus

Imagine we are afloat on a ship. We have brought enough spare parts to rebuild the whole ship. Over years we repair planks and sails, until eventually we have changed our whole ship. But we had to do it piecemeal, while sailing. There was no harbour to stop at to perform the work all at once like some Cartesian shipwright.

2 Descartes’ Method

Step I: We cannot know which of our beliefs are justified and which are not. So, we need a method to sort the good from the bad.

Step II: We cannot examine them one by one. Therefore, we must test the foundations of these beliefs.

Step III: To test the foundations of these beliefs, we must subject them to sceptical doubt.

Doubt 1.0

Optical Illusions and Perceptual Mistakes: How many of our beliefs are based on these mistakes? Is there any way to tell other than “demolishing them” as Descartes recommends?

Perceptual Mistakes

Phantom Limbs

Doubt 2.0

It seems we can always correct for the perceptual illusions and mistakes. In these cases we use other perceptions to determine what is illusory and what is real.

But what about cases where we cannot rely on any of our perceptions? This is where the Dreaming Scenario comes into play. In a dream, Descartes claims, we:

1) Have experiences that can vary wildly from our waking experiences, and,

2) We have no way of telling (Ever? Sometimes?) whether we are dreaming or are awake.

Do our dreams really reveal possible ways the world could be?

Are they that detailed and coherent?

If you might be dreaming even now, what might the waking world actually be like?

Would you want to get up?

You can check out any time you like, but you can never leave.

The strengths of the Dream Argument:

It is stronger argument against sense experience because

1) any given sense experience can be replicated in dreams

2) Hence sense experience is unreliable

3) In fact, there is never any sure way of distinguishing dreams from reality

Do dreams violate all the laws of the physical sciences?

Doubt 3.0

A priori may truths survive the Dream Argument: However different the physical laws of our dreams, Descartes claims that the geometry and mathematics of them are the same. This is because Descartes believes that the these are truths justified independently of experience – a priori – not justified by experience – a posteriori.

N.B. It turns out that since Descartes, we have learned that there are many possible geometries. It turns out that the universe nearly, but does not exactly, fit the geometry of Descartes day. Descartes thought wrongly someone could prove that parallel lines would never meet.

Different Possible Geometries of the Universe

Doubt 3.0

Could a deceiving God make you even you’re a priori judgements mistaken? How?

Possibility 1: God makes you so you cannot reliably make even basic arithmetical and geometric judgements. Does this even make sense?

Possibility 2: Every time you try your hardest to make one of these judgements, God interferes with the nerve connections so that you keep getting the wrong answer. Does this make more sense than the Possibility 1?

Could a deceiving God make these claims true?

2+2 = 3.145…

Squares have three sides.

Superman is and is not from Krypton.

The Cogito:

What is it to be a thinking thing?

Cogito ergo sum = I think therefore I am.

Is this true? Why or why not?

Arguments against the Cogito I

The Hidden Premise Criticism (HPC): This is an attack on the famous first form of the cogito argument, from the Discourses. This is where he says (in French) that “I think, therefore I am.”

The HPC claims that this phrase is a deductive argument, and that it has a hidden premise. Christoph Lichtenberg was the first to make this claim. He said the argue went like this:

1) I think

2) Thinking things exist.

3) Therefore, I exist.

Is Descartes entitled to (2) given his Doubt? Is he entitled to believe that any deductive argument escapes from the evil deceiver? After all, he can make us think that 2+2=5!

Arguments against the Cogito II:

Bertrand Russell thought that the Cogito was a deductive argument, but it was circular. He thought that the reason to believe that I thought was that I existed, and the reason to think that I existed was that I thought. It all made for a nasty circle.

Not a deductive argument.

Descartes seems to have rewritten the Cogito in the Meditations as “’I think’ is true whenever said by me” to make the point that it is not a deductive argument. It is something we simply see is true a priori.

It seems that 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. But…

Cotard’s Syndrome

Cotard’s Syndrome is an especially unusual psychiatric condition where there patient does not believe s/he exists. Since we are philosophers, we will not automatically assume they are wrong.

So, if someone did come to you honestly asserting “I do not exist,” what kind of mistake would they have made?

What does it mean for us to exist?

A Taster of Descartes Metaphysics

• Descartes is a Mind/Body Dualist. That means he believes that there are two fundamentally different kind of thing. There are material substances in the physical world. These include human bodies. Then there are spiritual substances, which include our minds.

• How does the Method of Doubt help us to draw this distinction?

From Doubt to Distinction:

Why Descartes thinks he is not his Body.

1) I can doubt the existence of anything that the Evil Deceiver (ED) could make me mistaken about.

2) ED could make me mistaken about the existence of my body.

3) ED could not make me mistaken about the existence of myself as a thinking thing right now.

4) I can doubt the existence of something iff that thing is not a necessary part of what I am.

5) Therefore, my body is not a necessary part of me.

6) Therefore, my existence as a thinking thing right now is a necessary part of me.

The Superman Objection (You can make your own)

The argument in the last slide uses a simple principle:

Epistemic Criterion of Identity: If I can doubt whether x is identical to y, then x is not identical to y. (Note: “Epistemic” means knowledge-based)

• Descartes applies this principle by arguing that, since he can doubt whether he is his body, he must not be identical to his body.

• But, as we all should know, many people in Metropolis doubted whether Superman was Clark Kent. But he was. So, the Epistemic Criterion must be false. But, before we abandon Dualism, let’s look at a stronger argument from later in the Meditations.

A Better Version of this Argument, from Meditations VI

1) If I can conceive of myself without x, then it is logically possible that x be separated from me.

2) If x can be separated from me, then x is not a necessary part of me.

3) I can conceive of myself without my body.

4) Therefore, it is logically possible that I can be separated from my body.

5) Therefore, my body is not a necessary part of me.

What’s with all the melting wax?

The WAX EXAMPLE is a demonstration of Descartes Rationalism.

Just as we used reason, independently of the senses, to establish that we are thinking things, we can use reason independently of the senses to establish fundamental facts about the physical world.

The Argument in the Wax Section

1) I have a clear and distinct idea of the wax as an extended substance.

2) This idea must either derive from my senses, my reason, or some combination.

3) The idea cannot derive from my senses, or my senses in combination with reason, because we retain the clear and distinct idea of the wax despite it undergoing a complete change of sensory properties (shape, smell, texture, colour, etc.).

4) Therefore, our clear and distinct idea of wax as an extended substance must derive from reason.

H2O

Compare the Wax example with learning that water – which can be a solid, a liquid, and a gas - is actually a compound of two different kinds of atoms, invisible to the naked eye.

And then learning that these in turn are made up of electrons and quarks, held together by the strong and electroweak forces.

And these be the three-dimensional parts of even smaller entities called strings whose vibrations in many dimensions give rise to matter in our world.

…

Primary and Secondary Qualities

The Wax Example is getting at a distinction that will latter be called the Primary/Secondary Quality Distinction:

Primary Qualities: Properties an object has independent of how it happens to affect our sense organs. In the case of the wax, for Descartes, the wax has the primary quality of being extended.

Secondary Qualities: Properties an object “has” solely in virtue of how it happens its primary qualities happen to affect us. In the wax example, the wax has many changing secondary qualities involving its smell, feel and colour.

Clear and Distinct Ideas and Truth

If an idea p is clear, then p is “present and manifest to the attentive mind.”

If an idea p is distinct, then p is “so separated from all other perceptions that it contains absolutely nothing except what is clear.”

Descartes goes on to claim that:

Everything that I very clearly and distinctly perceive is true.

Arguing for God’s Existence

Why argue for God’s existence?

We have been supposing that God could be a deceiver. If Descartes can establish that is indeed a God, and that God would not be a deceiver, then he will have shown that we can trust (some of) our judgments about the world.

Omnigod

Omnigod is a useful name for any God with the following perfections:

1) Perfect being: God is a necessary rather than a contingent being.

2) Perfect knowledge (omniscience)

3) Perfect goodness (omnibenevolence)

4) Perfect power (omnipotent)

The Trademark Argument

1) I have an idea of perfection2) This idea must have a cause. 3) The cause of this idea cannot be myself because I am imperfect.

4) Because of the Causal Adequacy Principle, the quality of the effect must exist in the cause.

5) Therefore a perfect being must exist.

Different Ways of Conceiving of Perfection

The Negative View. God’s perfection is what is left if you simply negate each of our imperfections. So, we have limited knowledge. God’s knowledge must not be limited in that way. We are limited in our power. God must not be circumscribed in the same manner.

Advantages of the Negative View

Advantages of the Negative View: We could create the idea of divine perfection from our idea of our own imperfection in one of two ways.

A) We simply negate the idea of imperfection, saying that perfection is whatever is not imperfect.

B)We construct the idea of perfection by taking our limited good features and imagining something with far better versions of them.

Evaluating the Negative View

Descartes’ Criticism of the Negative View: This is a purely negative conception of divine perfection. Our idea of divine perfection is positive. We think that God is complete perfection, what is left when we deny our imperfections.

In fact, Descartes argues that to know that we have an imperfection, we must already have an idea of perfection that we can judge ourselves against.

The Positive View of divine Perfections

The Positive View: divine perfection is not just a denial of imperfection, and so our knowledge of divine perfection cannot come from our knowledge of our imperfections. It must come from another source. Descartes argues that that source is God.

Thinking about Infinity

The difference between the Negative and Positive Views is similar that between two views of Infinity.

Potential Infinity: To say that the natural numbers (1,2,3…) are infinite is only to say that, for any number, we could add 1 to it. So, the set can grow, but there is not a complete set of all the natural numbers and anyway we could never grasp it. (This view invites the objection: How can something be potential if it can never be actual?)

Actual Infinity: On this view, there is indeed a set of infinite natural numbers and our minds can grasp the idea. Certainly, important parts of mathematics (and science) do not work without it.

The “Causal Adequacy Principle”

A cause must have at least as much reality as its effect.

Applied to our case, the cause of the idea of perfection must have at least as much reality as the idea of perfection itself.

The Trademark Argument

1. I have a clear and distinct idea of God as a perfect being.

2. This idea must have a cause.

3. The cause of this idea cannot be myself or anything in the world be they are imperfect.

4. The Causal Adequacy Principle: A cause must have at least as much reality as its effect.

5. Therefore, a perfect being must have caused my idea of God.

6. Therefore, a perfect being exists.

7. Since a perfect being would be benevolent, it would not be a deceiver.

The Proof for the Existence of Material Objects

1. I have ideas of material things.

2. The Causal Adequacy Principle: A Cause must have at least as much reality as its effect.

3. Argument by elimination: The ideas cannot come from me because they are produced without my co-operation and often against my will, not by God otherwise he would be a deceiver, so they must be produced by material things.

4. Therefore, material things exist

When can we rely on Sense Perception

1. God is not a deceiver.

2. Therefore, we will not go fundamentally wrong in our knowledge of the world if we form our clearest and most distinct perception of it.

3. As in the Wax Example, C&D Perception reveals that the material world consists of substances with their primary qualities.

4. Sense perception gives us a mistaken image of the world as containing secondary qualities as well.

5. There is no conflict between (4) and (1) because sense perception is just there to keep us from “harm.”

6. Constructing the World:

7. Descartes’ Foundationalism

Is there a Cartesian Circle?

These last arguments rely on the existence of God. Descartes’ arguments rely on clear and distinct ideas being true. Does Descartes need God to prove that clear and distinct ideas are indeed true? If so, then he is arguing in a circle. He uses C&D ideas to establish God’s existence, which is needed to establish C&D ideas.

If he is not doing this, why should we think clear and distinct ideas must be true? In other words, why should something in our heads (ideas that are clear and distinct) allow us to conclude anything about the existence of things outside our heads (God, material objects, etc.)