PHIL 101 Weeks 7 and 8
October 16, 2013
Justified True Belief:Account of Knowledge
For any subject S and any proposition P, S knows that P if and only if
(1) S believes P
(2) P is true
(3) S is justified in believing that P
(1) and (2) are not sufficient for knowledge
Because (1) could be founded on a random lucky guess
True beliefs without evidence don’t count as knowledge
Lucky guesses don’t count as knowledge
Believing truth for the wrong reasons (fancy talk from lawyer) is not knowledge
Argues that (1) (2) and (3) are not collectively sufficient for knowledge.
He presents a counter example to JTB:
Smith works in an office, has a generally reliable boss named Jones. One day, Jones comes into the office
and says, “Mary will get the promotion”
(a) Mary will get the promotion
Smith also discovers that Mary has 10 coins in her coat pocket. Smith infers that:
(b) The person who will get the promotion has 10 coins in their coat pocket
Smith has justified true belief for proposition (b)
It turns out that (b) is true, but it’s because Smith will get the promotion and also happens to have 10
coins in his coat pocket.
Smith has justified true proposition (b), But Smith doesn’t know claim (b). Therefore, counter example to
Russell’s Clock (another counter example)
In the past, the clock has been very reliable.
Today, as someone walks past, it says 12:20. That human believes it is 12:20. Furthermore, it is actually
12:20. BUT, suppose that the clock stopped exactly 24 hours ago.
Fair lottery, 1000 tickets.
You have ticket #203
You’re justified in believing that my ticket will lose. (are you really?) Suppose it is true, ticket 203 is a loser when they do the draw.
You have justified true belief in claim “my ticket will lose,” but you don’t know.
It looks like there should be a condition (3’) to the Justified True Belief system
(3’) It is impossible for S to be mistaken in believing P
Argument for Skepticism
About all a posteriori beliefs
Rappel: an a posteriori claim is one that is known or justified based on observations, on the senses
An a priori claim is one that, once you know the meanings, you don’t need to make observations to justify
One must take into account that sometimes the senses are mistaken; people can hallucinate, illusions can
(1) To know P, it must be impossible to be mistaken about P
(2) For all a posteriori P, it is possible to be mistaken
(C) Hence, one does not know any a posteriori P
Is Skepticism self-refuting?
I know that no one knows anything.
Weaker, but less contradictory: I know that no one knows anything a posteriori.
OR: Probably, no one knows anything
October 21, 2013
Introduction to Descartes
Rene Descartes: French philosopher and mathematician, often credited as the founder of the modern age.
The Copernican Revolution is the new belief that we revolve around the sun as opposed to the opposite.
Descartes questioned other notions in the minds of medieval humans, since several were starting to be
proven as wrong.
Geometry was a model for knowledge for Descartes.
Foundationalism is an approach to thinking about the structure of all our beliefs. We can model all our
knowledge on this picture if we think of the claims we are most certain of as our foundation.
The whole of philosophy is like a tree: the roots are metaphysics, the trunk is physics, and the branches
are the particular sciences (unity of knowledge, in contrast toAristotle).
(How can the roots be metaphysics? How can all knowledge be founded on metaphysics? How does he
Knowledge must be constructed from the bottom up, nothing can be taken as established until we get
back to first principles. Methodological doubt: He wants to systematically examine all of his beliefs (all kinds) and see which
ones can be the “axioms” (the foundations) of all our knowledge.
We need to categorize these beliefs into kinds.