Critical Thinking Lecture 7a Gettier By David Kelsey Defining Knowledge • Knowledge: – – We saw in lecture 7 that knowledge is more than mere belief or even mere true belief. Plato first defined knowledge as Justified True belief. Knowledge as JTB • Knowledge as JTB: – Thus, S knows that p if and only if: • S believes that p and • P is true and • S’s belief that p is justified – Individually Necessary: – Jointly sufficient: Gettier & Knowledge • Edmund Gettier – – – Born in 1927 Philosophy professor at University of Massachusetts Amherst since 1967 In his article Is Justified True Belief Knowledge? Gettier argues that something’s being justified true belief is not a sufficient condition for it’s being knowledge. • Thus, he argues that one can have a justified true belief and yet not have knowledge. • Gettier provides two counterexamples to prove his point. Smith, the job & 10 coins • • Smith, the job & 10 coins: – Smith believes that Jones is the man who will get the job and Jones has 10 coins in his pocket. • What is Smith’s justification for this belief? – So Smith infers that it is true that The man who will get the job has ten coins in his pocket. • What is Smith’s justification for this belief? – But Smith gets the job & he has 10 coins in his pocket So Smith has JTB without knowledge! The Ford & Barcelona • Now Smith gains evidence for the proposition: – That Jones owns a Ford (‘F’) • What’s Smith’s justification for this belief – So Smith Infers: Either Jones owns a Ford or Brown is in Barcelona. (‘A’) • What is Smith’s justification for this belief? – But Jones doesn’t own a Ford and Brown is in Barcelona • So Smith has JTB without knowledge again Replies to Gettier • Denying the assumptions: – He assumes that: • 1. It is possible for a person to be justified in believing a proposition that is false • 2. Closure: for any proposition P, if S is justified in believing P and – P entails Q & – S deduces Q from P & – S accepts Q as a result of this deduction, then – S is justified in believing Q. – Example: » Snowing so Freezing Denying Closure • Denying closure: – We could deny Closure by holding an Externalist theory of justification. – For the Externalist, justification comes not from an inner mental state at all. Instead, it is something external to your mind which confers justification on a belief. – An Example: • Reliabilism: a belief is justified if it is formed through a reliable belief forming process More replies to Gettier • Accepting the counterexamples: We might also reply to Gettier by accepting his counterexamples to the traditional definition of knowledge. – Finding another analysis: In this case we are then out to find a more adequate analysis of KNOWLEDGE. – Some examples: • Infallible justification • No false steps • No defeaters Last thoughts on defining knowledge • What Gettier shows is that there is a bigger problem with conceptual analysis • A possible reply: – concepts like knowledge have a graded nature