Full Idea
Two arguments against Megaran Actualism are that it turns powers into nomads: they come and go, depending on whether they are being exercised or not. And it stops us from distinguishing between unexercised powers and absent powers.
Gist of Idea
If powers only exist when actual, they seem to be nomadic, and indistinguishable from non-powers
Source
George Molnar (Powers [1998], 4.3.1)
Book Reference
Molnar,George: 'Powers: a study in metaphysics', ed/tr. Mumford,Stephen [OUP 2003], p.97
A Reaction
See Idea 11938 for Megaran Actualism. Molnar takes these objections to be fairly decisive, but if the Megarans are denying the existence of latent powers, they aren't going to be bothered by nomadism or the lack of distinction.
Related Idea
Idea 11938 The Megarans say something is only capable of something when it is actually doing it [Aristotle]