Full Idea
I take for granted that a disposition requires a causal basis: one has the disposition iff one has a property that occupies a certain causal role. Shall we then identify the disposition with its basis? That makes the disposition cause its manifestations.
Gist of Idea
A disposition needs a causal basis, a property in a certain causal role. Could the disposition be the property?
Source
David Lewis (Causal Explanation [1986], III)
Book Reference
Lewis,David: 'Philosophical Papers Vol.2' [OUP 1986], p.223
A Reaction
Introduce the concept of a 'power' and I see no problem with his proposal. Fundamental dispositions are powerful, and provide the causal basis for complex dispositions. Something had better be powerful.