In a broadcast talk delivered in 1956, the late J. L. Austin began by outlining to his listeners his now well-known concept of ‘the performative utterance and its infelicities’; and at the end of that first section of his talk he made this comment: ‘That equips us, we may suppose, with two shining new tools to crack the crib of reality maybe. It also equips us – it always does – with two shining new skids under our metaphysical feet’. In this talk I intend to illustrate a particular respect in which, in moral philosophy, the partial pessimism of Austin's comment has proved abundantly justified. I shall try to show how in this field one shining new tool has led in fact to the skidding of moral philosophers' feet – how one bright idea (an idea, as it happens, very closely akin to that which Austin himself was discussing) has led some influential theorists off in the wrong direction, and the rest of us back in the end, with rather little gained, to a position not far from that of our predecessors of about a hundred years ago. This dismal story, I should in justice make clear at the outset, is not that of the whole of moral philosophy, not even of moral philosophy in English; I shall be tracing only one out of several concurrent lines of thought, but the line which I shall trace will be, I think, readily recognised as having been, and perhaps as still being, more conspicuous than most.