Lesson 3 Skepticism

We'll begin with the Meditations  

What is epistemology?

episteme + logos 

Epistemology is the the study of things pertaining to knowledge.

 

What is knowledge?

Three kinds of knowledge.

I know my mother.

I know how to tie my shoes. 

I know that the France is in Europe. 

When 'that' follows 'know, a proposition tends to follow 'that.' 

I know that P. 

A proposition is a statement that is either true or false.  

The kind of knowledge that interests epistemologists is propositional knowledge. 

When is a proposition known? 

This is a matter of controversy (the subject of next class). 

According to a widely held view, knowledge is justified true belief. 

A person, S, knows a proposition, P, if and only if 

1. S believes that P. 
2. S is justified in believing that P. 
3. P is true.

(1), (2), and (3) are individually necessary and collectively sufficient. 

 

What is skepticism?

"Healthy" skepticism

This is the idea that one should be careful about what one believes. 

Skepticism about knowledge 

This is the idea that one cannot know propositions. 

Global skepticism 

This is the idea that one cannot know any propositions.

Local skepticism 

This is the idea that one cannot know some kinds of propositions. 

Skepticism about ethics,

Skepticism about other minds, 

Skepticism about the external world,

Skepticism about God, etc.

Skepticism about justification (rational belief)

This is the idea that one is not justified in believing propositions. 

This too might be sorted into global and local varieties. 

 

Skepticism about the external world

Some knowledge is based on experience. Some is not.

a priori knowledge does not depend on experience. 

All bachelors are male. 

A moon is a natural satelite.

a posteriori knowledge depends on experience.  

Jim is a bachelor. 

Saturn has 82 moons. 

 

Skepticism about the external world is skepticism about a posteriori knowledge.

Arguments for this often make use of skeptical hypotheses: 

possible scenarios on which one cannot tell whether propositions are true

Brain in a vat scenario.

Matrix scenario.

Descartes’s dream and evil genius scenarios

 

 The brain in a vat hypothesis

I do not know that I am not a brain in a vat that is being fed the "experiences" on which my beliefs about the external world are based. 

Although I do not have any reason to think that I am a brain in a vat, I cannot rule this it out because I my experience would be the same if it were true.

1. I know that I am not a brain in a vat only if I can tell whether I am a brain in a vat.
2. I cannot tell whether I am a brain in a vat.
3. Therefore, I do not know that I am not a brain in a vat.

If I do not know that I am not a brain in a vat, then I do not know whether my beliefs about the external world are true.

1. I can know that I have two hands only if I know that I am not a brain in a vat.
2. I do not know that I am not brain in a vat.
3. Therefore, I cannot know that I have two hands.

 

Some responses to the brain in a vat argument

“Here is a hand and here is another hand” (G. E. Moore).

I know that I have two hands, so I know that I am not a brain in a vat; although it remains true that I cannot tell that I am not a brain in a vat. 

But how does one know that one has two hands? 

 

Knowledge is not undercut by mere possibilities. 

 

The "little space ships" argument... 

 

The hypothesis is highly improblable and I have no reason at all to consider it.

Does the brain in a vat argument prove otherwise? 

One answer: If I believe that P is true, and P is true, and I came to believe that P is true in the right way, then I know that P is true even if I don’t know whether I came to believe that P is true in the right way. 

The idea: The way that I acquired my belief makes the difference. 

Does this answer help? What good is knowing if I don't know that I know?

 

Skepticism about rational belief

An argument is a set of premises meant to give a reason to believe a conclusion.

There are many kinds of arguments. 

Much of our reasoning from experience is in the form of inductive argument.

 

Inductive arguments are not meant to prove their conclusions, only to render them probable.

They purport to give reasons for generalizations or predictions.

1. The first swan I saw was white.
2. So was the second.
3. And also the one after that…
4. Therefore, all swans are white. (or the next swan I see will be white)

 Another...

1. The sun has come out every day thus far.
2. Therefore, the sun will come out tomorrow.

The fact that I have only seen white swans does not entail that all swans are white. 

The fact that the sun has always come out does not entail that it will do so tomorrow.

The argument is meant to give support, not a proof, for its conclusion.

 

 

But does it? David Hume thought otherwise. Our belief that the sun will rise tomorrow, he argued, is not justified at all. We have no reason to believe it.  

1. The sun has come out every day thus far.
   
2. ?
3. The sun will come out tomorrow.

Premise (1) does not by itself give a reason to believe (3). Something more is needed.

1. The sun has come out every day thus far.
2. The future will be like the past.
3. The sun will come out tomorrow.

Premise (1) gives a reason to believe (3) only if we have a reason to believe (2).

But what reason might we have to believe (2)?

We will need another argument. And it will have to be inductive.

1. The future has always been like the past.
2. ?
3. Therefore, the future will be like the past.

What will premise (2) have to be?