April 24, 2013, 6-7:30 PM in 234 Moses Hall

Adam Elga (Princeton University)

Crossword puzzles, fragmented belief, and logical omniscience

Is there an English word that ends in “MT”? (If you are stumped, think about the question for a moment and then read the last word of this abstract.) Before you figured out (or read) the answer to that question, did you know that the word that is the answer was an English word that ends in “MT”? In a sense, yes: the word was in your vocabulary. But in another sense, no: for a moment, you weren’t able to answer the puzzle question.

For finite agents, this phenomenon is unavoidable. Sometimes a piece of information is within one’s cognitive reach for some purposes but not for others. So a state of mind should be represented not by a single batch of information, but rather by a specification of what information is within cognitive reach for what purposes.

Representing states of mind in this way helps in understanding inconsistent or fragmented states of mind: sometimes incompatible bits of information (or misinformation) are within reach for different purposes. It helps in explaining what happens during “aha!” moments in reasoning: one’s cognitive reach is expanded. And it lends support to an attractive solution of the problem of logical omniscience. In presenting this theory of mental representation, we hope to convince you that it is more fruitful than you may have dreamt.

(This is joint work with Agustin Rayo.)