Full Idea
Solidity is the effect of a power of repulsion between whole things, and shape is the effect of a power of attraction between parts of whole things.
Gist of Idea
Solidity comes from the power of repulsion, and shape from the power of attraction
Source
Harré,R./Madden,E.H. (Causal Powers [1975], 9.II.B)
Book Reference
Harré,R/Madden,E.H.: 'Causal Powers: A Theory of Natural Necessity' [Blackwell 1975], p.172
A Reaction
This sounds a bit too neat in its division, but it shows nicely how a metaphysics with powers can deal with categorical properties. The question, remains, though of what is doing the repelling and attracting. Fields, they say.