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Chapter 6

How Can We Know about the External World?, Descartes’s Meditation I

Professor Lund’s slides with supplemental material from Core Questions in Philosophy

Story from Chapter 6 Introduction

You know that the Earth is round, that penguins inhabit Antarctica, and that some trees shed their leaves in the fall.

But what if your whole life has just been a vivid dream, the Earth never existed, and you are simply an android?

How can you know that this is false?

Positions on the External World

We should start our inquiry about what we can know by doubting everything that can be doubted.

Our senses cannot provide us with knowledge that objects continue to exist when not perceived, or that they exist apart from perceiving minds.

We should dismiss the skeptical hypothesis since it is simple to account for the existence of the external world through sense data.

We should accept that the world is real because this gives us a better explanation of the available evidence than its skeptical rival.

Kant's claim that we cannot know things in themselves should not lead us to skepticism.

A General Skeptical Argument

A skeptical hypothesis

The world is different from how you take it to be.

Appearance vs. Reality

https://https://youtu.be/sRt1WiCNrxc(Pink dots)

https://www.youtube.com/watch?v=kz5VdpUVeuM (Mosquito noise)

http://webexhibits.org/causesofcolor/2D.html (Red/green color perception)

The gap between subjective and objective

We’re denying the claim that “appearance is reality” or to put it another way, we think that how things seem is not always how they really are.

Think of the phrase “appearances can be deceiving.”

The External World

We often assume that there is a reality independent of our minds.

Our mind contains beliefs, beliefs that are supposed to model the world outside our mind. However, this model in our minds is imperfect.

Representational thought: to RE-present the world to ourselves.

General Skeptical Hypotheses

There are several global skeptical hypotheses.

The Android Hypothesis: you are a dreaming android, and everything you believe that you know is false; the Earth does not exist, there are no penguins in Antarctica, and no trees to lose their leaves in the fall.

The Demon Hypothesis: you are systematically deceived by an evil demon, and so almost everything you believe that you know is false.

The Brain in a Vat Hypothesis: you are simply a brain in a vat, and all of your experiences are the result of electrical stimulation.

Local Skeptical Hypotheses

Skeptical hypotheses need not be global in scope. They could be local.

No Other Minds Hypothesis: you are the only creature with a mind.

Unexpected Future Hypothesis: the future is radically different from the past.

Who’s Descartes?

One of the most important figures in Western Philosophy

You may be familiar with his work if you have ever mapped Cartesian points

As a philosopher, mathematician, and scientist, he was very concerned by the idea that no belief amounts to knowledge

In his Meditations, he sets out to test all of his beliefs for the possibility of error

Preview: Descartes’s Meditations

Descartes doubts everything that can be doubted.

He notes that all of his sensory experiences could be instilled in him by a demon who is trying to delude him.

Since this is possible, Descartes believes that he should be skeptical about everything that he believes that he knows about the external world.

In this way Descartes uses the Demon Hypothesis to generate global skepticism about the external world.

We can identify with Descartes

He puts off the project of questioning his beliefs for as long as he possibly can

He grew up believing a lot of things that now that he is older, he recognizes might not be true

Why might they be false?

We have Knowledge Gaps

For example, what’s a “Xing”?

http://www.npr.org/2011/07/05/137443123/i-was-absent-that-day

Descartes recognizes that many of his basic assumptions, if mistaken, would have a “house of cards” effect, toppling many other of his beliefs

Descartes vs. The Skeptics

Think of Descartes as Jackie Chan (or your favorite martial artist) and the Philosophical Skeptics as some of his adversaries

Descartes is going to try and defeat them with their own method, the method of doubt

Which of our beliefs could be wrong?

Descartes agrees with the skeptics that many of the beliefs that we are most committed to are vulnerable to error

Where do you live?

What’s your name?

Are you asleep or awake?

All of our answers to this question could be wrong

Descartes is a Foundationalist

To understand why his theory is called foundationalism, ask yourself: What is a foundation?

It’s a base that holds up other structures.

Think of a concrete-block basement that supports the higher floors of a house

The basement represents foundational beliefs—beliefs we don’t ordinarily think about, but which on which our other everyday beliefs depend

The higher floors are the “superstructure,” and they represent our everyday beliefs (where we live)

The superstructure depends on the foundation, without it, the superstructure would collapse

Analogy to Geometry

In geometric proofs there are a set of axioms or “givens,” which are simple and typically thought of as obvious or self-evident

The purpose of a geometric proof is to derive theorems (new conclusions) from the axioms

Descartes’s strategy for knowledge is modeled after geometric reasoning

The Method of Doubt

Descartes is looking to see whether he can discover any beliefs that could serve as the foundation for our everyday beliefs

He chooses to test every belief by seeing if it can be doubted

Remember, he is trying to prove the skeptics wrong

He does this by doubting even more beliefs than the skeptics do

Test for Indubitability

He’s not checking to see which beliefs are ACTUALLY false; instead he’s checking to see whether any given belief could possibly be false.

If a belief might be false, then it is not a candidate for a foundational belief

Two types of indubitability:

Psychological: we can’t get ourselves to doubt a belief (flip side of Pascal’s wager)

Logical: we cannot doubt the belief without running into a logical contradiction

Efficient: Test beliefs by category

A posteriori beliefs (see glossary): Any belief that depends upon or comes after a particular experience is a posteriori. This category includes ALL beliefs that depend upon our faculties of perception.

What does a trumpet sound like?

What does the color red look like?

What do olives taste like?

What does an ocean breeze feel like?

Any belief in this entire category could be wrong, so no foundational beliefs here

What’s left?

Empiricists believe that all of our beliefs about the world require experience, so they would say nothing is left.

A useful reference point here may be Locke’s tabula rasa or blank slate

Rationalists argue that many of our beliefs do not depend upon a particular experience.

Dr. Lund is a rationalist, so is Descartes

A priori beliefs

An a priori belief can be discovered through reason alone or without relying on any particular experience

Think of what you could figure out in a sensory deprivation tank

2+2=4

A bachelor is an unmarried male

A triangle has 180° interior angles

Key here is that these ideas are not dependent upon any particular experience.

In fact, the specific ways we learn these ideas just serve as props for us to get these concepts

The Helen Keller test: there are many beliefs she could acquire despite being completely deaf and blind. In fact, she earned a Master’s Degree.

A priori beliefs are foundational?

No, Descartes says that all of the beliefs in this category are vulnerable to error.

This is where he presents his evil demon scenario

Think of someone like a computer programmer, except that programmer hard-wired your mind

Could that individual have wired your mind so that you always make an incorrect conclusion?

Descartes thinks the answer is certainly yes

What is left now?

It seems like these two categories exhaust all the beliefs that our mind contains

Descartes says there is another category we’ve overlooked

Cogito, Ergo Sum fits in to this last category

I think, therefore I am

This claim may sound too simple to be useful here, but it is extremely powerful

P1: I think

C: I am

Descartes argues that the act of thinking confirms an individual’s existence

It is a deductively valid argument with a true premise

Even if we change the first premise to “I doubt,” it still demands the truth of the conclusion

Not even a skeptic can doubt his or her own existence during the time that they are thinking

A Foundational Belief!

We must exist as a thinking thing in order to think or doubt

So what is beyond any logical doubt? That we do exist in some fashion

We discover this through introspection (looking within our own minds and observing what is happening there)

Appearance and Reality again

Descartes is NOT arguing that things always are as they seem to be

Instead he is arguing that in this one case, if we are experiencing any conscious thoughts, then we must exist as a thinking thing

If we can have perceptions, we have to exist to experience those perceptions

We are the final authority on the appearance, not the reality

Descartes argues that no-one knows better than you do how things seem to you

If a Dr. gives you a hallucinogenic drug, she cannot dispute you when you say:

“I seem to see a pink elephant in the corner of my hospital room”

She can disagree if you insist that there is a pink elephant in the hospital room

In other words, the only thing we have special access to is how things look to us, not how they really are

How do we know we have a headache?

The Home Headache Test: http://snltranscripts.jt.org/94/94ahht.phtml

The feeling of pain we call a headache is only a sensation—so no one besides us can tell whether or not we are experiencing headache pain.

First-Person Psychological Reports – Knowledge about our Internal World

Statements that start “I seem to see” have the following structure:

First-person: “I”

Psychological Report: “seem to see” (reports on your own state of mind, not the world outside of it)

Interesting side concern: Descartes thought ALL such reports were infalliable

So, “I seem to be in pain” = “I am in pain”

“I seem to be in love”=“I am in love”

Different than “It seems to me to be sunny” which ≠ “It is sunny”

How do we get to Knowledge of the External World?

Since knowledge is a relationship between what we think is true and what the facts are in reality, Descartes has left us hanging

He still needs to link our rock-solid belief, “I am thinking,” to ordinary beliefs such as “I really am awake right now.”

If you have a great roof on your house but it is not strapped on to the rest of your house, it won’t do you much good in a hurricane

Another Foundational Belief?

“God exists and is no deceiver”

Should seem like a shocking choice for Descartes to pick this as a foundational belief

Why does he claim this is beyond any possible logical doubt? That’s a story for another day.

What does he get out of this claim: the idea that any beliefs in our heads that are “clear and distinct” are accurate reflections of the external world

Let’s see how this would work

P1: I seem to see a slide in front of me (Foundational)

P2: My beliefs that there is a slide in front of me is clear and distinct (Foundational, knowable through introspection)

P3: Clear and distinct ideas are true (Foundational)

C: There is a slide in front of me

Notice that this process internally certifies a belief as knowledge by looking inside one’s mind for the characteristics that are the hallmarks of knowledge.

No knowledge is possible without a process of introspection (looking within one’s own mind)

Begging the Question

Another name for Circular reasoning is Begging the Question

It’s a fallacy

So calling this the Cartesian Circle is not a compliment to Descartes

Example of this fallacy: My college and the professors I had changed the world by changing my life. Then I graduated and changed the world. My college should keep graduating students who change the world, therefore they should stop graduating students who become professors.

The Cartesian Circle

God exists and is no deceiver

We get to the conclusion that God exists using clear and distinct ideas

Clear and distinct ideas are true because God guarantees the truth of certain ideas

Summary

Descartes proved the skeptics wrong: there is at least one belief that is beyond any possible logical doubt, as shown by the Cogito argument

Descartes promised we could count our everyday beliefs about how the world outside our minds is as knowledge

On this point, it looks like the skeptics won