Full Idea
There is no metaphysical justification whatever for treating the solid, bounded, material object as the determiner of all thing concepts. Fluids are no less material things than are hard solid blocks.
Gist of Idea
Hard individual blocks don't fix what 'things' are; fluids are no less material things
Source
Harré,R./Madden,E.H. (Causal Powers [1975], 9.IV)
Book Reference
Harré,R/Madden,E.H.: 'Causal Powers: A Theory of Natural Necessity' [Blackwell 1975], p.180
A Reaction
We don't tend to talk of a fluid as 'a' thing, and without distinct objects there would be virtually no structure, or interest, in nature, so what gives identity to the blocks must interest the metaphysician.