PHLA10H3 Lecture Notes - Lecture 2: Omnibenevolence, Omnipotence, Fallacy
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Exercise 2 it: here"s a little logical puzzle: you are in a strange land where everyone is either a knight or a knave. Knights always tell the truth; knaves always lie. You meet two of them, a and b. Prove it: a is a knave, because if he was a knight, the statement we are both knaves would be false. Since a is a knave, he is lying when he says that we are both knaves , meaning that b is a knight. There is a single day that is everybody"s birthday. This is not true because not everyone has a birthday on the same day. This is a mistaken belief: what is the valid deductive logical form of a reductio ad absurdum argument, if p is false, then a is true. Explain in terms of possible worlds: a necessary being is something that must exist in all worlds .
