  Hence, while many writers have come to the defense of external reasons by appealing to a disposition to be motivated by beliefs about reasons, if this interpretation is correct then Williams’ argument is directly aimed against this kind of solution. A disposition of this kind could explain why a consideration R could motivate an agent once he believed that it was a reason to act, but it could not make it the case that R itself was a genuine explanation of his acting, and therefore a reason for him to act. To use Williams’ own example, if Owen Wingrave comes to believe that the fact that military service is a family tradition is a reason for him to enlist, that belief may indeed motivate him to enlist, and explain his doing so. But if he has no desires or dispositions that would cause the belief that military service is a family tradition itself to motivate him to enlist, then the fact that military service is a family tradition cannot itself be a genuine explanation of his enlisting, and therefore his belief that it is a reason for him to enlist is false.