Philosophers and others have often debated whether we have freewill: i.e. whether (in a sense I shall try to elucidate) our power to choose between X and Y is radically undetermined, so that if we choose X we yet might have chosen Y, and vice versa. My concern is not with that question but with a hypothetical one which arises from it: if we had such freewill, what implications, if any, would, that fact have for the sciences. My argument concentrates on the social sciences, since the phenomena with which they deal inevitably involves human choice.