introphil_lecture_slides_IntroPhil2-week2-slides
.pdfKnowledge and Certainty
Question: If knowledge entails truth, then does it also entail certainty or infallibility (i.e., does it rule out any possibility of error)?
Answer: No. That knowledge entails truth only means that you can’t know a falsehood. The truth can be known in a fallible way.
11
Knowledge and Certainty: An Example
Do you know what you had for breakfast this morning?
But are you certain about this? Isn’t it possible that you have made a mistake?
The moral: while knowledge demands truth, it doesn’t require certainty (any more than it requires infallibility).
12
Knowledge and Probability
Knowing that a proposition is true is not the same as knowing that this proposition is probable.
Compare:
•I know that human beings have been to the moon.
•I know that it is likely/probable that human beings have been to the moon.
The second claim is not equivalent to the first but much weaker (it implies doubt about whether human beings have been to the moon).
13
Knowing versus Getting it Right
There is more to knowledge than mere true belief. One can get it right in lots of ways which wouldn’t suffice for knowledge.
Example: A juror believes the defendant is guilty purely out of prejudice. As it happens, he is right. But clearly he does not know that the defendant is guilty.
14
Two Intuitions About Knowledge
The Ability Intuition |
The Anti-Luck Intuition |
Knowledge requires |
Knowledge requires |
getting it right through |
getting it right in a non- |
one’s ability |
lucky way |
15
Part One Conclusions
•One core usage of ‘knowledge’ is propositional knowledge (i.e., knowledge-that).
•Two basic conditions for propositional knowledge are that one believes the proposition, and that the proposition must be true.
•But there is more to knowledge than mere true belief.
16
Part Two:
The Gettier Problem
17
The Classical Account of
Knowledge
Plato (427-347 BC)
One can know a proposition if, only if:
(i)That proposition is true;
(ii)One believes that proposition;
(iii) One’s belief is justified.
18
Gettier
Counterexamples
Edmund Gettier (b. 1927)
Examples of justified true belief where the true belief in question is just too lucky to count as knowledge
19
A Gettier-Style Case
The Stopped Clock
You believe that the time is 7.28am.
You are justified in believing that the time is 7.28am.
It is true that it is 7.28am.
But you don’t know that it’s 7.28am because, unbeknownst to you, what you are looking at is a stopped clock.
A stopped clock, yesterday.
20