Full Idea
As the most promising candidate for entities which intrinsically qualify as ultimate because their nature is in principle identical with their powers we will offer a physical field.
Gist of Idea
Maybe a physical field qualifies as ultimate, if its nature is identical with its powers
Source
Harré,R./Madden,E.H. (Causal Powers [1975], 8.VII)
Book Reference
Harré,R/Madden,E.H.: 'Causal Powers: A Theory of Natural Necessity' [Blackwell 1975], p.155
A Reaction
An electron comes fairly close to being nothing but a bundle of powers, but fields seem to have a slightly more basic role in physics, so this strikes me as a good suggestion. It meets Ladyman's mocking of the 'microbangings' view.