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What Is Knowledge?
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What Is Knowledge?Slide2

“What Is” Questions

Philosophers are often concerned with “what is” questions: what is the mind? What is moral goodness? What is truth? What is beauty? What is knowledge?Slide3


Here we want to know the essence of these things. When we ask “What is

moral goodness?”

we don’t mean “Which things are good?” but

Why are


things good?”

“What is it about them that

makes them good


“What is the essence of moral goodness?”Slide4

Why Should We Care?

Not all questions about essences are interesting or worth caring about.

“What is the essence of garbage?”

“In virtue of what is something a table?”

Philosophers don’t answer those questions. But they do care about knowledge. Why?Slide5

Some Reasons…

“There is only one good, knowledge” ~Socrates

“Knowledge is the food of the soul” ~Plato

“All men by nature desire knowledge” ~Aristotle

Knowledge is power”

~Thomas Hobbes

“The only fence against the world is a thorough knowledge of it” ~John LockeSlide6

More Recently

Recently, some philosophers have defended two other claims about the central importance of knowledge:

Knowledge is the norm of assertion. (Stanley and Williamson)

Knowledge is the norm of action. (Hawthorne and Stanley)Slide7

The Beginnings of Western Philosophy

Western philosophy, like much of Western culture, and Western literary and artistic traditions, traces its history back to ancient Greece. Slide8

Thales (624-546 BCE)

Thales of Miletus was the first philosopher, according to Aristotle, and is sometimes considered the first scientist (and even the first mathematician), because he tried to give

natural explanations

(as opposed to mythological or supernatural explanations) of things, based on

general principles

, which he supported with

reasons and arguments

(and not just things he made up). Slide9

Socrates (469-399 BCE)

Socrates was a philosopher in Athens during a period of political turmoil.

Socrates left no written work, and all that we know about his views is from dialogues written by his students Plato and Xenophon, comments by Aristotle, as well as comic plays by Aristophanes that poke fun at him.Slide10

The Wisest Man

One day, one of Socrates’ friends


went to the Oracle at Delphi (a prophecy speaking priestess at the temple of Apollo), and asked her whether there was anyone wiser than Socrates in all of Athens.

She said ‘no.’ This surprised Socrates, because he believed he had no wisdom at all.Slide11

Athens’ Gadfly

Socrates set out to test the Oracle’s claim by seeking out the people he thought should be wise in Athens. If he could find that they had any wisdom at all, he would know her claim was false. What he discovered by questioning all these people was that even though they claimed to know a lot,

none of them knew anything

. His great discovery was that he was wise, because unlike them

he knew that he knew nothing


The Socratic Method

Socrates’ method was not to argue for or against any position (remember, he didn’t believe he knew anything), but rather to tease out other people’s beliefs through careful questioning, and then to lead them to realize that their beliefs were wrong– again, by forcing them to answer questions that they hadn’t considered. Slide13

Plato (424-348 BCE)

Plato is often considered the greatest Western philosopher of all time (and his usual competition for #1 is his student, Aristotle).


once said, “the European philosophical

tradition… consists

of a series of footnotes to

Plato.” Slide14

Plato and Socrates

Plato was a young follower of Socrates. After the death of Socrates, Plato wrote dialogues where Socrates was the main character and Plato (in the few times where he was present) never spoke. Slide15

The Literary Socrates

There are lots of reasons to suppose that the literary character Socrates who appears in Plato’s dialogues is not presenting views or arguments that Socrates presented, and over the course of Plato’s life, the views the literary Socrates expresses change and grow. But the literary Socrates is not just Plato. Aristotle says that Plato had an “unwritten doctrine”– his true beliefs– which he refused to write down.Slide16


Plato’s dialogues are named after the main character that Socrates has a discussion with in the dialogue. The Theaetetus is a dialogue in which Socrates talks with Theaetetus.


is regarded as Plato’s best dialogue on epistemology (the theory of knowledge), and sometimes his best dialogue simpliciter.Slide17

Three Theories of Knowledge

In the dialogue, Plato asks Theaetetus, a young Greek mathematician, and also his mentor


, another mathematician, what the essence of knowledge is: “What is knowledge?”

Theaetetus proposes three theories of the essence of knowledge, and by the end of the dialogue, all of them are rejected.Slide18


and Propositional Knowledge

In English, there are (at least) two grammatically distinct constructions involving know.


knowledge, knowing a person, a thing, or a place: “I know Professor Lau.”

Propositional knowledge, knowing a fact: “I know that Professor Lau has hair.”Slide19


In French, for instance, different verbs are used for the different senses of ‘know’:


’ is used for


knowledge: ‘




Toulouse’– I know Toulouse.

‘Savoir’ is used for propositional knowledge: ‘

Je sais qu'il l'a

fait’– I know






Possible Confusion

Socrates and Theaetetus often don’t make a distinction between the different kinds of knowledge. Greek doesn’t have a strong grammatical distinction between the two kinds of ‘know’ so Socrates and Theaetetus may have thought that we needed to give one account that applied to both kinds at once (rather than treating them as different things).Slide21

One Non-Theory

Theaetetus’ first attempt at answering the question “What is knowledge?” is to list the different kinds of things that are knowledge:

Geometry is knowledge, carpentry is knowledge, animal husbandry is knowledge…Slide22

Essence, N

ot Examples

This is unacceptable, because remember we want to know the


of knowledge,

not examples

of knowledge.

We want to know


geometry, for example, is knowledge;

in virtue of what

carpentry is knowledge;

what makes it true

that animal husbandry is knowledge, and so forth.Slide23

A Comparison

Socrates compares Theaetetus’ proposal to a proposed definition of ‘clay’ that goes: “there’s the clay of sculptors, and the clay of potters, and the clay of brick makers…”

This doesn’t help anyone who doesn’t already know what clay is. It doesn’t tell us what it is about a thing that makes that thing clay.Slide24

First Definition

What Socrates wants is a definition of clay. If something fits the definition, then it is knowledge, and if it does not fit the definition, it is not knowledge.

Theaetetus first attempt at a definition is:

Knowledge = perceptionSlide25

Protagoras (490-420 BCE)

Socrates thinks that this definition is close to the beliefs of Protagoras, another Greek philosopher, who was the mentor of


(Theaetetus’ mentor).

Protagoras was famous for his claim that “

Man is the measure of

all things

: of things which are, that they are, and of things which are not, that they are not”Slide26

Truth Relativism

Protagoras’ doctrine is a version of truth relativism, the idea that there are no absolute truths, only truths relative to this person or truths relative to that person.

It might feel cold to you and not cold to me; then it was true

relative to you

that it was cold, and not true

relative to me

that it was cold.Slide27

K = P and Truth Relativism

Truth relativism is not a view about knowledge (although Protagoras and Heraclitus both held the view that knowledge = perception).

The relevance here is that the claim that knowledge = perception entails truth relativism, given the principle: If you know something, then it is true.Slide28


I might feel cold while you do not feel cold.

Therefore, perception is person relative.

Knowledge = perception.

Therefore, knowledge is person relative.

Whatever is known is true.

Therefore, truth is person relative.Slide29

Heraclitus (535-475 BCE)

Socrates, in attempt to explain how truth relativism can be made sense of, brings in some ideas of Heraclitus.

Heraclitus is a mysterious philosopher whose work does not survive. He is known as believing things like ‘Everything flows’; ‘You can never step into the same river twice’; and ‘The path up is the same as the path down.’Slide30

Everything Flows

Here’s how Socrates thinks these ideas can be employed:

Nothing is ever in a fixed state of being. Instead, everything is constantly changing or becoming something else. When I perceive a thing, it becomes one thing, and when you perceive it, it becomes something else.Slide31

Nothing IS

So there is no point in saying what a thing is, for it is never any one thing, but becomes many.

And there is no point in saying what it becomes, for it becomes something for me and a different thing to you.

Everything is flux, and thus perceptions of different people are always different, and so what is known is always different.Slide32

The Dream Objection

Socrates proposes an objection to the knowledge = perception thesis.

If knowledge = perception, then knowledge of existence = perception of existence. But in dreams we

perceive things as real

that we (when we are awake)

know are not real

, like dragons and monsters. Slide33

Nothing IS

Later, Socrates recognizes that this objection doesn’t work, at least if Heraclitus is right.


including ourselves

, merely is. We do not continue existing when we dream but become something else, which is also unstable and changing. Relative to that thing, the objects of dreams are true.Slide34

Disanalogies between Knowledge and Perception

Socrates outlines some disanalogies:

Perception comes in degrees of sharpness and intensity, knowledge doesn’t.

Perception varies with distance from the object perceived, knowledge doesn’t.

You can see something and not hear it (perceive it and not perceive it) but not know something and not know that thing.Slide35

We’re All Equal Knowers

And he makes three points about what knowledge = perception entails:

Animals are just as knowledgeable as humans, what they perceive is true for them.

Humans are just as knowledgeable as gods, for both perceive their own truth.

Protagoras is just as knowledgeable as any man off the street.Slide36

Why Are Relativists Philosophers?

Of course, Protagoras is not going to deny either (1) or (2). His theory commits him to those beliefs, and there’s nothing contradictory with holding them.

But if he also believes (3), why does he teach philosophy? If everyone already knows what’s true-for-them, what can they possibly gain by listening to him?Slide37

Protagoras Responds

Socrates imagines a response: the purpose of philosophy is not to give people truth who believe falsehoods, because everyone has what’s true for him. The purpose of philosophy is therapeutic: for some people, what’s true is awful, because what they believe is awful. The philosopher’s goal is to make what they believe good, and thus what is true-for-them good.Slide38

Absolute Goodness, Relative Truth

The response involves accepting an

absolutism about what is good or beneficial

(even while it maintains a relativism about truth).

If what is beneficial is relative, then changing the beliefs of others is only good relative to some philosophers, while it is bad relative to other philosophers. Slide39

The Real Protagoras

Protagoras actually did hold the view (when he was alive) that benefit was absolute, while truth was relative.

There are some reasons to go this way. If benefit was relative, then suppose you thought it would help you get an A (benefit your goals) to drink beer and not study. Then relative to you, that would help. But that’s absurd!Slide40


Suppose that it is absolutely beneficial to believe in truth relativism (TR).

Then relative to anyone, it is beneficial to believe in TR.

But someone could believe that it is not beneficial to believe in TR.

This belief would be true for that person.

So relative to them, belief in TR is not beneficial.Slide41

A Second Contradiction?

TR says that truth is

absolutely relative

: truth is relative to every individual person.

But clearly someone could believe that TR is not true.

Then according to TR, that belief is true-for-them.

So relative to them, TR is not true.

So TR is not true of some people.Slide42

Final Objection to Protagoras

Protagoras seems to have a problem with the future.

If what I believe to be true is true for me, then my beliefs about the future are true for me.

So suppose I believe that Tuesday. I’ll win the lottery; then it’s true for me that I’ll win Tues.

But when Tuesday. rolls around, I don’t win. Now it’s true for me that I don’t win on Tuesday.Slide43

Summary: Argument against Protagoras

Knowledge and perception are


in many ways.

K = P entails truth-relativism (TR): if we believe it, it’s true-for-us.

TR entails the relativity of goodness or benefit.

TR is self-contradictory or self-defeating.

TR is incompatible with the intuitive fact that we can believe false things about the future.Slide44

Final Objection to Heraclitus

According to the theory of Heraclitus, everything flows, and is constantly changing.

This means, for example, that white things are always changing to different colored things.

But it must also mean that knowledge flows and is constantly changing.

So we shouldn’t say: knowledge = perception, because it will change and ≠ perception.Slide45

Final Objection to K = P

There are some things that we know, that are not things we can perceive.

Sameness and difference: we know our


are different from our hearings, but we don’t perceive this, because none of the senses both sees and hears.

We know mathematical truths, but we don’t perceive “all triangles have 3 sides.”Slide46

Final Objection Continued

3. Good and evil: you can see an action, but you cannot see that it is good. However, you can know that some things are good.

4. Essences: if it were possible to perceive what the essence of knowledge is, then we wouldn’t need to do philosophy. We’d just need to look for, or smell, or taste the right answer. But we assume we can know the essence.Slide47

Definition Number 2!

After all that, Theaetetus is now asked if knowledge is not the same as perception, what is knowledge?

Theaetetus makes a new proposal:

Knowledge = true beliefSlide48

The Main Issue

If knowledge = true belief, then since some beliefs we have are known and other beliefs we have are not known, there must be a distinction between true and false beliefs.

The main issue that Socrates is concerned with is

how are false beliefs possible


Anything I Can Think, I Know

If I don't know a thing, I can't think about it.

So, if I can think about it, I know


If I know it, I know its


If I know its essence, I can't be wrong about


So anything I can think about, I have only true beliefs about


Therefore, I cannot have false beliefs.Slide50

Faulty Premise

The most natural place to find an error in this argument is in the premise that if you know the essence of a thing, you can’t be wrong about it.

I can know for example, that goodness = what the gods love, but not know that helping others is good, because I don’t know if the gods love helping others.Slide51

Second Puzzle

If you see, hear, smell, or taste something, it exists


Thought is


perception: instead of seeing external things, you ‘see things in your mind.’

How can you think about something

, ‘see it in your mind’

and yet that something be nothing?

And if it is nothing, and you think of nothing, then aren't you

not even


Faulty Premise

Here, the problem seems to be that thought and perception are


in this way. I can think about things that don’t exist, like Santa Claus.

Additionally, we might think that some false things exist (propositions). I might believe the proposition that it is Tuesday, and that proposition exists, even though it is Monday.Slide53

Two Lessons

The point is not that Socrates thinks these are good arguments.

Instead, we have learned two important things about what must be true for false belief to be possible:

1. We must be able to be wrong about things whose essences we know.Slide54

Two Lessons

The point is not that Socrates thinks these are good arguments.

Instead, we have learned two important things about what must be true for false belief to be possible:

2. Either we are able to think about non-existent things, or some false things must exist.Slide55

Lacking a Model

We must ask ourselves, however, what sort of account can abide by these lessons?

An overly empiricist account, where knowledge is


perception ‘in the mind’ will obviously not work.

In abandoning knowledge = perception for knowledge = true belief, we have abandoned our only clear


of how things worked.Slide56

Lacking a Model

Knowledge = perception told us how the mind relates to what is known– through perception.

The model doesn’t work: we can’t perceive essences or non-existent things, but the mind can relate to those things.

Knowledge = true belief is not a new model, because it does not explain how the mind relates to what it believes.Slide57

Argument against D2

Still, Socrates thinks knowledge ≠ true belief.

Suppose there has been a murder, and no eye-witnesses

Suppose the jury is superstitious, and I convince them that X is guilty, b/c I dreamed that he


No one is inclined to say that the jury


that X

is the


But if I was accidentally right, they will have a true belief that X is the


True Beliefs, Bad Reasons

Here the important point is that a belief that is true, but which you believe for bad reasons, is not really knowledge.

If you believe something because you want to, or because your horoscope says it, or because a really unreliable person told it to you, then you don’t know it.Slide59

Definition 3

In the third definition Theaetetus just tries to fix the account he just gave.

He says that knowledge = true belief + a justification.

(Notice that this still does not provide an alternative


to perception.)Slide60

The Rest



keeps going, but a lot of philosophers think it is not entirely serious.

The conclusion involves Socrates rejecting knowledge = true belief + a justification, even though there are lots of other dialogues where Plato/ Socrates seem sympathetic to this view.Slide61

The Preferred Version

Plato’s preferred version (it seems) was that knowledge = true belief + a justification for that belief.

The versions of “+ a justification” in the


are different from this view and Socrates rejects them all.Slide62


Plato’s motive would be that he didn’t want Socrates to appear to agree to anything positive, because that wasn’t Socrates’ style.

But he also wanted to come as close as possible to what he (Plato) thought was the truth, so that the audience would accept the correct theory (Plato’s).Slide63


Whether that’s true or not, what is true is that for most of the rest of Western philosophy, this was the standard view of knowledge:

Knowledge = true belief, with a justification that supports that belief.Slide64

Essence of Justification

A lot of the literature on the theory of knowledge has focused on not “What is knowledge?” but, assuming that knowledge = justified true belief, has focused on “What is justification?”

Various theories have been proposed, sometimes at great levels of detail…Slide65



is a theory of justification that says something roughly like the following:

Subject S knows proposition P =

P is true.

S believes P.

S’s belief is based on evidence E that makes P highly probable.Slide66

Less and More

Some philosophers have argued that the definition of knowledge needs less in it, and some have argued that it needs more.

In the ‘less’ camp, David Lewis suggests that you can know something without believing it. Maybe you know the answer in class, but are too self-doubting to believe what you know!Slide67

Russell’s Stopped Clock

Here’s a case that argues that we need more.

Every day when you walk to work, you pass by a clock that has been exactly on time for 100 years running.

Unknown to you, last night it was struck by lightning and stopped at 8:00.

When you walk by at 8:00 AM exactly, you look at the clock and believe “it is 8:00 AM.”Slide68

JTB Not Sufficient for Knowledge

It seems as though:

You believe it is 8:00 AM.

Your belief is true: it is 8:00 AM.

You are justified in believing it is 8:00 AM.

(For example, it is highly probable that given that the clock says it’s 8:00 AM, it is in fact 8:00 AM.)


do not know

it is 8:00 AM.Slide69

JTB + What?

Since the 1970’s, philosophers have made many attempts to add something to Plato’s account that will avoid Russell’s stopped clock case, and other cases like it (often called


cases, after the man who first brought them to everyone’s attention).

No one has yet succeeded in a way that is satisfactory to everyone else.Slide70

A New Movement

One direction people have considered going recently is rejecting the idea that there can be a


of knowledge.

The “knowledge first” movement says that instead of understanding knowledge in terms of belief and justification, we should understand belief and justification in terms of knowledge.Slide71

In Summary

Philosophers have long felt that knowledge is one of the most important things to understand.

No account of what knowledge is has “stood the test of time” and convinced a majority of philosophers of its truth.

Some people have begun to speculate that knowledge can only be understood on its own terms, not in terms of something else.

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What Is Knowledge? - Description

What Is Questions Philosophers are often concerned with what is questions what is the mind What is moral goodness What is truth What is beauty What is knowledge Essences Here we want to know the essence of these things When we ask What is ID: 130503 Download Presentation

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