  Externalists reject this picture, contending that one can have reasons for action that are independent of one’s prior motivations. They typically agree that practical reasoning is capable of generating new motivations and actions. They agree, in other words, that if agent s has reason to do x, it must be possible for s to acquire the motivation to x through reflection on the relevant reasons. But they deny that such reasoning must in any significant way be constrained by s’s subjective motivations prior to the episode of reasoning.  On this approach, practical reason is not conceived merely as a capacity for working out the implications of one’s existing desires and commitments; it equally involves the capacity to reason about what it would objectively be good to do, and to act on the basis of this kind of evaluative reflection.  Normative reflection is thus taken to be independent of one’s prior motivations, and capable of opening up new motivational possibilities (Parfit 1997).