33 Fatalism

Just the Arguments pp.125-127

Let p be: “It is going to rain tomorrow” (or whatever declarative sentence that describes an event that you think that can happen tomorrow).
P1. If it is true now that p, then necessarily p.
P2. If it is true now that not p, then necessarily not p.
P3. It is true now that p or it is true now that not p.
C1. Necessarily p or necessarily not p (constructive dilemma, P1, P2, P3).

この論証は間違っている。それは、P1とP2の曖昧さに起因する。

“If X, then, necessarily Y.” This can be interpreted as (a) “It is a necessary truth that if X, then Y” or as (b) “If X, then it is a necessary truth that Y.” On the one hand, if premises 1 and 2 are read as (a), they are clearly true but, then, the conclusion doesn’t follow from premises. On the other hand, if premises 1 and 2 are interpreted as (b), the conclusion does follow from them, but they presuppose fatalism. So, either the argument is not logically valid or it begs the question.