unit 8: knowledge

Unit 8: Knowledge

Chris HeathwoodOffice: Hellems 192

Office Hours: Monday 10-1

[email protected]

What We’ll Cover in Unit 8

I. The Nature of Knowledge

A. What is a theory of knowledge?

B. Plato on Knowledge

1. Theaetetus’ Theory of Knowledge

2. Socrates’ Refutation of Theaetetus

3. Plato’s Theory of Knowledge

C. Gettier’s Refutation of Plato

II. Hume’s Problem of Induction

The Three Fundamental Questions of Philosophy

1. What is there?

2. What should I do?

3. How can I know?

(Metaphysics)

(Ethics)

(Epistemology)

Some Questions in Epistemology

1. What is knowledge?

2. What is epistemic justification?

3. What are the fundamental sources of knowledge?

4. What are the limits of human knowledge?

5. What is the status of skepticism?

The Nature of Knowledge

What Is Knowledge?

• Putting the question this way makes the question sound really hard. Here are two other ways to put it:– “What is it to know something?”– “Under what conditions is it true that a person

qualifies as knowing that something is the case?”

• An answer to this question will be a theory of knowledge.

What is a theory of knowledge?

A theory of knowledge is a statement of the conditions under which a person knows that something is the case.

It is a statement of this form:

S knows that p if and only if ____________ .

Theories are knowledge are supposed to reveal the

nature of knowledge.

Further Clarification of the Question ‘What is Knowledge?’Three ways the word ‘knows’ is used:

• “Bob knows how to ride a bicycle.”

• “Bob knows the president of the U.S.”

• “Bob knows that the earth is round.”

The theories of knowledge we are interested in here are about the third kind of knowledge – called knowledge that, or propositional knowledge.

How Do We Go About Constructing (and then Evaluating) a Theory of

Knowledge?

Analogy: Bachelorhood.What is bachelorhood?What is it to be a bachelor?What are the conditions under which a person qualifies as a bachelor?What a “theory of bachelorhood” looks like: x is a bachelor if and only if __________.

The Socratic Method, or the Method of Counterexamples

• A generalization is proposed

• We try to come up with a “counterexample” to it – i.e., a concrete example that “counters”, or shows false, the generalization just proposed

• If we do, we have refuted the generalization

(but we might use the counterexample to help us improve on the generalization just refuted)

• If we can’t, the generalization might be true.

Plato (428-347 BC)

• The best known ancient Greek philosopher

• Student of Socrates; teacher of Aristotle• Wrote about 23 philosophical dialogues• Famous doctrine: the Theory of the

Forms• Western philosophy “consists of a

series of footnotes to Plato.” - A. N. Whitehead (1929)

excerpt from the

Theaetetus

by

Plato

translated by F.M. Cornford

Socrates: Well, that is precisely what I am puzzled about. I cannot make out to my own satisfaction what knowledge is. Can we answer that question. What do you think?

Socrates: But the question you were asked, Theaetetus, was not, what are the objects of knowledge, nor yet now many sorts of knowledge there are. We did not want to count them, but to find out what the thing itself – knowledge – is. Is there nothing to that?

Theaetetus: No, you are quite right. …

Socrates: Then tell me, what definition can we give with the least risk of contradicting ourselves?

Theaetetus: The one we tried before, Socrates. I have nothing else to suggest.

Socrates: What was that?

Theaetetus: That true belief is knowledge. Surely there can at least be no mistake in believing what is true and the consequences are always satisfactory.

Theaetetus’ Theory of Knowledge

The True Belief Theory:

S knows that p if and only if

(i) S believes that p; and

(ii) p is true.

Socrates’ Argument Againstthe True Belief Theory

Soc: You will find a whole profession to prove that true belief is not knowledge. …

The profession of those paragons of intellect known as orators and lawyers. There you have men who use their skill to produce conviction, not by instruction, but by making people believe whatever they want them to believe. You can hardly imagine teachers so clever as to be able, in the short time allowed by the clock, to instruct their hearers thoroughly in the true facts of a case of robbery or other violence which those hearers had not witnessed. …

… when a jury is rightly convinced of facts which can be known only by an eyewitness, then, judging by hearsay and accepting a true belief, they are judging without knowledge, although, if they find the right verdict, their conviction is correct …

But if true belief and knowledge were the same thing, the best of jurymen could never have a correct belief without knowledge. It now appears that they must be different things.

Socrates’ Argument Against The True Belief Theory

The Argument

1. If the True Belief Theory is true, then the jury knows that I committed the crime.

2. But they don’t know I committed the crime.

3. Therefore, the True Belief Theory is not true.

Further Counterexamples to the True Belief Theory of Knowledge:

a. My belief that our football team will win their next game.b. Groundhog’s Day example.

Each case shows that true belief is not sufficient for knowledge.

The Lesson:

a belief that is truejust because of luck does not

qualify as knowledge.

Plato’s Theory of Knowledge

Socrates: So when a man gets a hold of the true notion of something without an account, his mind does think truly of it, but he does not know it, for if one cannot give and receive an account of a thing, one has no knowledge of that thing. But when he also has got hold of an account, all this becomes possible to him and he is fully equipped with knowledge. … a true notion with the addition of an account is knowledge?

Plato’s Theory of Knowledge

The JTB Theory


(i) S believes that p;

(ii) p is true; and

(iii) S is justified in believing that p.

Comments About the JTB Theory

a. How it avoids the counterexamples to the True Belief Theory

b. Theory of Justification still needed.

c. Some possible ways to be justified in believing something:

i. perception iv. testimony

ii. introspection v. induction

iii. memory vi. deduction

d. Theory accepted for thousands of years.

e. Theory no longer accepted today.

Gettier’s Refutation of Plato

Edmund Gettier (1927- )

• Not the best known contemporary American philosopher, but pretty well known.

• Student of his teachers at Cornell; teacher of me at UMass.

• Wrote just one 3-page paper.• Famous doctrine: Justified true belief ain’t

knowledge.• A. N. Whitehead (1929) probably didn’t say

anything about Gettier.• Really good at badminton.

A Gettier-Style Counterexample

STEP 1:

Suppose I see your driver’s license, an Alaska driver’s license.

This seems to justify me in believing

(1) that you are from Alaska.


STEP 2:On the basis of my belief

(1) that you are from Alaska

I infer

(2) that someone in this class is from Alaska.

Because I am justified in believing (1), and because (2) follows from (1), I am justified in believing (2).


STEP 3:The driver’s license I saw is actually a fake

ID: you are not from Alaska.

Hence, the following belief of mine is false: (1) that you are from Alaska.Note:• I have a false justified belief in (1).• The JTB Theory thus far implies, correctly,

that I do not know (1).


STEP 4:Just by chance, someone else in the class is from Alaska!

Hence, my belief

(2) that someone in this class is from Alaska

is true!


STEP 5:Consider (2): (2) Someone in this class is from Alaska.Some questions:

Is (2) true? YESDo I believe (2)? YESAm I justified in believing (2)? YES

Do I know (2)? NO

JTB ≠ Knowledge


In the form of a little argument …

1. If the JTB Theory is true, then I know that someone in our class is from Alaska.

2. But it’s not true that I know that someone in our class is from Alaska.

3. Therefore, the JTB Theory is not true.

Other Gettier-Style Examples

• The Hallucination

• Russell’s Clock

• The Sheep in the Field

A Way to Save the JTB Theory

• Note that what all the examples have in common: the subject has highly reliable, but not infallible, evidence for the proposition believed.

• To say that e is infallible evidence for p is to say that e entails p.

• Recall that Gettier’s argument assumed that a person can be justified in believing something without having infallible evidence for it.

What is Knowledge?


(i) S believes that p

(ii) p is true

(iii) S is justified in believing that p

(iv) the Gettier Condition (what is it?)

unit 8: knowledge

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