 This thesis that what motivates us to act is always a desire should be accepted only if we have a good understanding of what a desire is. If a desire is simply identified with whatever internal state moves someone to act, then the claim, “what motivates us to act is always a desire”, when spelled out more fully, is a tautology. It says: “the internal state that moves us to act is always the internal state that moves us to act”. That is not a substantive insight into human psychology, but a statement of identity, of the form “A = A”. We might have thought we were learning something about what causes action by being told, “what motivates people is always a desire”, but if “desire” is just a term for whatever it is that motivates us, we are learning nothing (see Nagel 1970: 27–32).