Full Idea
Dispositional properties deserve special mention since they seem to be properties that have modal consequences - consequences for what properties the individuals that instantiate them would have in counterfactual circumstances.
Gist of Idea
Dispositions have modal properties, of which properties things would have counterfactually
Source
Robert C. Stalnaker (Mere Possibilities [2012], 3.4)
Book Reference
Stalnaker,Robert C.: 'Mere Possibilities' [Princeton 2012], p.60
A Reaction
I take this to be the key idea in trying to understand modality, but Stalnaker makes this point and then moves swiftly on, because it is so far away from his possible worlds models, in which he has invested a lifetime.