Here is a simple thought that I think is worth taking very seriously.
The following three things are different, one from another:
- (1) powers;
- (2) essences;
- (3) causal necessitation.
Andrea comments below that he would add “dispositions” to the list. I agree that an unexercised power is not the same as an exercised power. I’m also willing to think that the very distinction between potentiality and actuality is not itself the same thing as a power-to-do — though what the distinction “is,” I’m not sure.
Still, I think I’d be more inclined to add “the very distinction between potentiality and actuality” to the list than to say that a disposition, in virtue of referring to an unexpressed power, is something different from a power.
Andrea? Others? I’ll respond in “Comments” from here on, if we want to have more discussion.