Intellectual historiography as it has commonly been practised is devoted to the formidability of tradition. It seeks to identify enduring suppositions - world-pictures, cosmological principles, models of nature, mind, time, and God - and to view their elasticity over great expanses of cultural history. It does not shy away from apparent examples of radical change. Indeed, some of these examples are its stock subjects - the seeming break between Christianity and antiquity, the rise of scientific empiricism, the self-proclaimed specialness of the various romanticisms. But, armed with concepts such as the 'unit ideas' of Arthur O. Lovejoy and the 'reoccupied positions' of Hans Blumenberg, intellectual historians have generally preferred to craft stories about gradual renovation and substitution rather than rupture and novelty. It is telling in this respect that in The Legitimacy of the Modern Age, a work of tremendous scope and originality, and probably the most distinguished contribution to intellectual history in recent years, Blumenberg should keep returning to the oddly provincial point that the idea of progress does not derive from a secularization of Christian history: for a historian of ideas, the challenge of modernity is to get straight on its tradition. It can sometimes seem, in the light of this discipline, as if the course of Western thought were the internal conversation among fifty or so intellectuals dedicated to solving each other's problems while doomed to pass on new versions of them. This vision of thinking as the grandest of human games, self-generated and self-regulating, is responsible for a marked decline today in the authority of classical intellectual history. At the extreme of this suspicion, in the popular new Marxisms, the entire project of intellectual history, the boundary that constitutes its subject matter, appears wishful. Intellect is too flimsy and extravagant, too uneconomical, to have so grim and massive a thing as a history. Ideas are the forms ideology takes when forgetful of its purpose, and intellectual history dissolves into the forces at work in history at large.