By invoking surprising rationalist considerations that Bernard Williams does not anticipate, this paper defends Williams’s claim that that moral criticism on the basis of purported external reasons amounts to ‘bluff’. After strengthening this rejection of external reasons by drawing parallels to compelling rationalist arguments in other domains, the paper mounts a similarly rationalist critique of internal reasons invoked by Kantian moral philosophers. The paper closes with an apocalyptic line of thought that develops the preceding rationalist arguments into a challenge to (...) the notion of acting for reasons in general. (shrink)