Full Idea
The idea of a disposition occupying a different causal role involves a conceptual confusion, ...but there is no conceptual or logical absurdity in a categorical base occupying a different causal role.
Gist of Idea
Unlike categorical bases, dispositions necessarily occupy a particular causal role
Source
Stephen Mumford (Dispositions [1998], 07.3)
Book Reference
Mumford,Stephen: 'Dispositions' [OUP 1998], p.149
A Reaction
This is the core of Mumford's theory of dispositions. I'm beginning to think that dispositions are merely ways we have of describing and labelling functional mechanisms, and so 'dispositions' drop out of the final story.