Full Idea
Scholastics reject anything like bare dispositions, on Aristotelian principles. Powers are forms, and forms actualise their subject, and are causally efficacious. Therefore no powers can be bare dispositions.
Gist of Idea
Scholastics reject dispositions, because they are not actual, as forms require
Source
Robert Pasnau (Metaphysical Themes 1274-1671 [2011], 23.5)
Book Reference
Pasnau,Robert: 'Metaphysical Themes 1274-1671' [OUP 2011], p.535
A Reaction
The point seems to be that a mere disposition is not actual, as a form is required to be. I would have thought that a power does not have to be operational to be actual. A live electric wire is a real phenomenon. It isn't waiting to be live.