gettier: is justified true belief knowledge? · gettier case 1: jones, smith, and the job interview...

Review Preliminaries Case 1 Case 2 General remarks Replies

Gettier: Is Justified True Belief Knowledge?

Gettier: Is Justified True Belief Knowledge? March 7, 2014


Overview I

Review

Preliminaries

Case 1

Case 2

General remarks

Replies



Knowledge as Justified True Belief

The JTB Account of Knowledge‘S knows that p’ is true if and only if:

1 p is true (false propositions cannot be known)2 S believes that p (if S doesn’t even believe that p, then

obviously S cannot know that p)3 S’s belief in p is justified (it is not merely a result of luck)

Gettier’s thesis: This is not su�cient (= we can have (1)–(3)while still not having knowledge).



Preliminaries

Fallibility: we can justifiably believe something that is in factfalse.

Example:I am justified in believing that my brother is in Switzerland at themoment, although it very well might be that he is not.

Transitivity of justification: If S is justifiably believes P,and P entails Q, and S knows that P entails Q, then Sjustifiably believes Q.

Example:If I am justified in believing that my brother is in Switzerland atthe moment, and I also know that Switzerland is in Europe, then Iam justified in believing that my brother is in Europe.



Gettier Case 1: Jones, Smith, and the Job Interview




Smith has justified belief in the following:1 Jones is the one who will get the job (Justification:

overhearing the boss)2 Jones has ten coins in his pocket (Justification: S has seen it)

Therefore, Smith has also justified belief in:

“The guy who will get the job has ten coins in his pocket” (from(1) and (2), by transitivity of justification).

As it turns out:1 Smith gets the job2 Smith happens to have 10 coins in his pocket




In this case, S:

1 had a belief2 S’s belief was true3 S’s belief was justified

However, S still did not haveknowledge!

This means that we have a case where S satisfied the JTBdefinition of knowledge, and still did not have knowledgeTherefore, the JTB definition is too broad.



Gettier Case 2: Smith, Jones, Brown, and the Ford

Smith has justified belief in the following:1 Jones owns a Ford. (Justification: he has always owned one,

and S saw him driving a Ford yesterday)Therefore, Smith has also justified belief in:

“Either Jones owns a Ford, or Brown is in Boston” (from (1), bytransitivity of justification, and since whenever “Jones owns aFord” is true, “Either Jones owns a Ford, or Brown is in Boston” isalso true).

As it turns out:1 Jones does NOT own a Ford2 Brown happens to be in Boston indeed.



Gettier Case 2: Smith, Jones, Brown, and the Ford

In this case, S:

1 had a belief2 S’s belief was true3 S’s belief was justified

However, S still did not haveknowledge!

This means that we have another case where S satisfied theJTB definition of knowledge, and still did not have knowledge.Therefore, the JTB definition is too broad.



Some General Remarks

A definition is supposed to give a necessary and su�cientcondition for the thing defined.One counter-example is enough to refute a definitionCommon in the Gettier-cases:

we have justified belief in somethingthe belief is in fact truebut it is not true by the reasons we thought it was true — wewere gettierized!



Some Possible Replies to Gettier:

Supplement the JTB account with some extra conditionGive up the justification condition and replace it withsomething else that worksGive up one or both of the initial assumptions (fallibility,transitivity of justification)


gettier: is justified true belief knowledge? · gettier case 1: jones, smith, and the job interview...

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