Sentences of the forms ‘A has a reason to φ’ or ‘There is a reason for A to φ’ (where ‘φ’ stands in for some verb of action) seem on the face of it to have two different sorts of interpretation. On the first, the truth of the sentence implies, very roughly, that A has some motive which will be served or furthered by his φ-ing, and if this turns out not to be so the sentence is false: there is a condition relating to the agent's aims, and if this is not satisfied it is not true to say, on this interpretation, that he has a reason to φ. On the second interpretation, there is no such condition, and the reason-sentence will not be falsified by the absence of an appropriate motive. I shall call the first the ‘internal’, the second the ‘external’, interpretation. (Given two such interpretations, and the two forms of sentence quoted, it is reasonable to suppose that the first sentence more naturally collects the internal interpretation, and the second the external, but it would be wrong to suggest that either form of words admits only one of the interpretations.)

I shall also for convenience refer sometimes to ‘internal reasons’ and ‘external reasons’, as I do in the title, but this is to be taken only as a convenience.