Lately I’ve been assembling materials for a contrast between two different “root metaphors” that have been used in making sense of life, the world, and things — one a notion of form associated especially with Aristotle, and the other a Latin scholastic and modern notion of action. This is also related to the historical transformation of the notion of efficient cause and of causality in general.
The first thing to note is that these are families of metaphors rather than uniform applications of the “same” two concepts. Literal shapes, linguistic meanings, and patterns of activity are all called “forms”, but do not reflect the same concept. The “action” of creation from nothing and that of mechanical impulse are two entirely different concepts.
The unifying themes, I think, are that “action” is supposed to be something more or less simple, immediate, and instantaneous, supporting what is supposed to be a kind of bottom-up, foundational explanation of things, whereas “form” always involves some “intensional” complexity and mediation; may involve extension in time and space that further ramifies that intensional complexity and mediation; and supports a kind of “middle-out” explanation that begins with reflection on middle-sized elements of actual experience, rather than a posited foundation of ultimate simple constituents.
(For some additional complications regarding the above simple picture of action, see A Thomistic Grammar of Action.)
The Postmodern Peripatetic 