Thursday, January 6, 2011

Epistemology: Gettier on Justified True Belief (First Case)

Knowledge and knowing are terms that we may use on a regular basis in our daily lives.  We say, “I know a lot of people who live in Irvine.”, “I know my boyfriend loves me.” and “I know how to drive a car.”  These statements display the diverse ways that we use the term in everyday speech.   In this class, however, knowledge is used as a technical term.

In the philosophical tradition, knowledge has been defined as justified true belief.  A statement (or proposition), is only knowledge, if (1) it is a belief, (2) that belief is true and (3) that true belief is justified.  In other words, these three conditions are each individually necessary and when combined together, sufficient for a proposition to be knowledge.

Gettier came up with two counterexamples to this definition of knowledge.

First Gettier Case.  Smith and Jones are competing for a job.  Smith has good reason to think that Jones will get the job and he has good reason to believe that Jones has ten coins in his pocket.  From this, he infers simply that “The man who gets the job has ten coins in his pocket.”  It turns out, Smith gets the job instead of Jones.  Also, it just so happens that Smith also has ten coins in his pocket.  When Smith did not know yet that he himself got the job, he had a true and justified belief “The man who gets the job has ten coins in his pocket.”, even though this true belief was based on Smith thinking that Jones would get the job.  Gettier says that we cannot call this justified true belief knowledge!

Gettier’s Assumptions.  (1) One can be justified to believe false propositions.  (2) If Smith is justified in believing P and Q can be deduced from P (P logically entails Q), then S is also justified in believing Q.

The Gettier Problem.  Gettier shows that justified true beliefs are not sufficient  for knowledge.  This is because one can have a justified true belief by mere luck.  If one only has a justified and true belief by luck, this is not knowledge (says Gettier)!  Another problem is that if we were to look across many possible worlds where minor relevant details are changed, such as a world where Jones has a hole in his pocket and so he only has nine coins because one has fallen out, it would not always be the case that both (1) Smith believes that the man who gets the job has ten coins in his pocket and (2) it is true that the man who gets the job has ten coins in his pocket.  In the possible world where Jones has a hole in his pocket, for example, Smith will still have the belief but the belief will be false.  Gettier thinks that a justified and true belief is not knowledge if in very similar possible worlds the belief is false or the belief is not believed.  This is what is meant by saying that the truth and belief fail to covary across possible worlds.

Think of the following situation.  A little boy named Timmy sees his mother kissing Santa Claus, or rather, his father in a Santa Claus costume.  Timmy believes he saw mommy kissing Santa Claus.  Because he has justified belief that Santa is a different person from his father, he is also justified when he believes that his mother is kissing someone other than his father.  Now, say that it just so happens that Timmy’s mom really is cheating on Timmy’s dad (with someone other than Santa who Timmy knows nothing about).  We would say that when Timmy believes that his mother is cheating on his father, he has a belief that is both true and justified.  However, because his belief is only true by chance, Timmy has no knowledge!

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