Since its publication in 1979, Bernard Williams' "Internal and External Reasons" has been one of the most influential and widely discussed papers in ethics. I suggest here that the paper's argument has nevertheless been universally misunderstood. On the standard interpretation, his argument—which he subsequently elaborated and defended in further discussions—is perplexingly weak. In the first section I sketch this Standard (or, more provocatively, "Supposed") argument, and detail just how terrible it is. The badness of the argument itself may not be (...) a conclusive reason not to ascribe it even to a great philosopher—perhaps every philosopher is guilty of having offered some terrible arguments—but Williams himself seems to point out blithely the very flaws that make it so terrible, making the standard reading difficult to justify. The second section proposes an interpretation on which he offers an Alternative (or, more provocatively, the "Actual") argument, one which is immune to the objections that seem fatal to the Standard argument. On this interpretation, better supported by the textual evidence and the principle of charity, Williams' conclusion seems to follow validly from defensible premises, including a substantive and interesting analysis of the concept of a normative reason. (shrink)