General Philosophy Lectures HT 2009

THE DEFINITION OF KNOWLEDGE

What is knowledge? Can we define knowledge, or define what it is to know something?

The traditional account of knowledge—as discussed since Plato’s time (if not before)—is that it

requires: a state of mind (a belief), a condition in the world (that belief’s being true), and a further

condition qualifying that true belief (that it be justified and not just a lucky guess). Which led to the

suggestion that knowledge can be defined as Justified True Belief. That is:

Subject S knows that P if and only if: (1) P is true;

(2) S believes that P;

(3) S is justified in believing that P.

This is known as the Tripartite Definition of Knowledge (since it has 3 parts). According to its

supporters, the tripartite definition provides individually necessary and jointly sufficient conditions

for a subject knowing a proposition P.

(Note that this definition is concerned with knowledge that something is the case, or that some fact

or proposition obtains. There may be other kinds of knowledge—in particular, knowing how to do

something, such as speak a language or drive a car, and knowledge by acquaintance (immediate

recognitional knowledge, perhaps of one’s own psychological states)—which are untouched by this

definition, except if they are ultimately entirely dependent upon knowing that. Some philosophers

think, however, that the dependence runs the other way around; that is, that knowing that something

is the case is ultimately dependent upon knowing how to do certain things.)

Objections to the Tripartite Definition

Standard objections to the above definition take two forms:

Is each of the three clauses of the Tripartite Definition necessary to know P?

Are the conditions 1 – 3 jointly sufficient for knowledge?

You might also wonder whether knowledge is the type of phenomenon which is amenable to

definition in the first place, but that discussion will be postponed until the attempts to produce a

definition have been explored.

The first kind of objection to justified true belief being a strict definition of knowledge is that

meeting all three conditions is not even a necessary condition for knowledge. For instance, it is not

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absolutely obvious that knowing something implies believing it: in certain circumstances it might

not be nonsensical to say ‘I know that Q, but I don’t believe that Q’.

Also, what should we say about cases in which the subject appears to know something that has

subsequently turned out to be false. There are plenty of examples like this in the History of Science:

did Newton know the laws of motion he discovered (which are not universally true)? According to

the definition of knowledge above, he can’t have done because the laws (and much of the rest of his

theory) are strictly false in modern physics. (In which case, what chance is there for our current

scientific theories being true?) But, if we can’t know scientific facts, what can we know? The

definition may be too strong.

The Gettier Problem

Edmund Gettier produced some famous examples which showed that fulfilling the 3 conditions

above is not sufficient for knowledge. (See the reading for plenty more examples, but one is

provided below...)

Smith and Jones are both about to be interviewed for a particular job. Smith has good reason to

believe that Jones will get the job (he is the Managing Director’s son, has better qualifications and

more experience than Smith etc.). Smith has also just seen Smith count the coins in his pocket and

there are 10 of them in there.

On this basis, Smith has good reason to believe the proposition that:

(GB1) Jones will get the job and Jones has 10 coins in his pocket.

Which allows Smith to infer that:

(GB2) The man who will get the job has 10 coins in his pocket.

But now, imagine the scenario that Smith is the one who actually gets the job and Jones

(unbeknownst to him at the time) has 10 coins in his pocket. So (GB2) is true, Smith believes it, and

he’s justified in believing it. But (GB2) wouldn’t count as knowledge, so the tripartite definition is

not sufficient.

Responses to Gettier

There are three kinds of responses to the Gettier Problem:

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a) Find a reason that the counterexamples do not work;

b) Add another condition to make the Tripartite Definition work;

c) Explicate some of the concepts in the Tripartite definition in order to avoid the counterexamples.

Several responses to Gettier fall under (b):

i) Relevant falsehood . The examples rely upon a proposition being inferred from a false belief:

if we can eliminate such false beliefs, and not justify other beliefs on the basis of them, we

would avoid having justified beliefs of the type which do not count as knowledge.

ii) Reliability of Method (see Armstrong) The Gettier examples rely upon the subject having

the ‘wrong sort’ of justification. If we restricted justified true propositions to those which we

justified according to a reliable method, we would avoid Gettier type situations.

iii) Defeasibility . Justification in the case of belief is defeasible; that is, the presence of certain

truths (and the subject’s learning about such truths) would remove the justification in the

Gettier examples and so they would not be problematic cases. Justification of knowledge

must be indefeasible

iv) .Causal Theory of Knowledge (see Goldman) The tripartite definition needs to be

supplemented with a causal constraint: P’s being true causes the subject’s belief that P (or,

the fact that P causes S to believe P). This would clarify the reliable method required in (ii)

and accord with naturalistic views about how our senses work (and thus how we acquire

knowledge).

There are (of course) difficulties with these responses to Gettier. These vary in strength according to

whether they can work at all, or whether they can successfully give an account of all types of

knowledge.

Alternatively, responses of type (c) attempt to revise or further explain the concepts involved in the

tripartite definition in order to avoid the Gettier problem. One group of such responses explicates

the notion of justification which has been rather neglected until now (this is important in its own

right, whether or not one thinks that knowledge can be defined).

In particular, one could argue that someone is justified (or not justified) in holding each belief that

they have, but crucially that she might not know whether she is; that is, whether or not a subject is

justified is not always something the subject is aware of. So you don’t always know that you know

P. This view is called externalism (to be contrasted with internalism which is such that the subject

does know that she knows that P in every case). This view may also come in handy when

combatting the problems raised by the radical sceptic.

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