Full Idea
Whenever someone does something for a reason he can be characterised as (a) having some sort of pro attitude towards action of a certain kind, and (b) believing (or knowing, perceiving, noticing, remembering) that his action is of that kind.
Gist of Idea
Acting for a reason is a combination of a pro attitude, and a belief that the action is appropriate
Source
Donald Davidson (Action, Reasons and Causes [1963], p.3-4), quoted by Rowland Stout - Action 3 'The belief-'
Book Reference
Stout,Rowland: 'Action' [Acumen 2005], p.34
A Reaction
This is the earlier Davidson roughly endorsing the traditional belief-desire account of action. He is giving a reductive account of reasons. Deciding reasons were not reducible may have led him to property dualism.