  Reid's argument does not decisively settle the question of whether or not human conduct comes about in accordance with laws linking it to prior motives. Rather, what he has shown is that we cannot accept the claim that human conduct is law governed through simple reflection from the armchair. We do need to do careful conceptual work in order to provide a non-trivial definition of strength that is different from either the animal or rational definitions; but we also need to do careful empirical work in behavioral psychology in order to determine if people do, indeed, always act on the strongest of motives in the sense of strength that we develop. His argument, then, makes a contribution to the question of whether or not people are the efficient causes of their own behavior by posing a further, and difficult problem for those, like Hume, who deny it on the grounds that our behavior is law-governed.