Full Idea
There is no a priori necessity for supposing that all disposition properties must have a 'categorical base'. In particular, there may be some mental dispositions which are ultimate.
Gist of Idea
Some dispositional properties (such as mental ones) may have no categorical base
Source
H.H. Price (Thinking and Experience [1953], Ch.XI)
Book Reference
Price,H.H.: 'Thinking and Experience' [Hutchinson 1953], p.322
A Reaction
I take the notion that mental dispositions could be ultimate as rather old-fashioned, but I agree with the notion that dispositions might be more fundamental that categorical (actual) properties. Personally I like 'powers'.