The weakest point in this version of Williams’ argument is probably its fundamental, conceptual premise: that the concept of a practical reason is the concept of an explanation of action under certain conditions. Even if we grant the controversial claim that the concept of a practical reason is the concept of an explanation we can still resist this analysis. Suppose, for example, that the concept of a reason to do A is the concept of an explanation of why to do A, or of why doing A is a good thi