Analytic philosophy has a complex history of more than one hundred years and this movement is so variegated that it can hardly be characterized by a single feature. Most of those who have tried to do so either were not aware of its diversity or considered only some part of its history. For example, it is sometimes believed that analytic philosophy is committed to a thoroughly anti-metaphysical stance. Such a belief may be rooted in some of the famous pronouncements of the logical empiricists, in the philosophical method put forward by Wittgenstein in his Tractatus Logico-philosophicus, or in the fact that some of the works of early analytic philosophy due to Russell and Moore – two of the founding fathers of the movement – have usually been interpreted as reactions against Bradley's metaphysics and other versions of the British idealism of the time. Other facts, however, which support a completely different view, should not be overlooked. For one thing, Russell's theory of the proposition and his logical atomism, as well as his philosophy of logic, clearly had metaphysical implications. For another, the logical empiricists' anti-metaphysical crusade, which had been forceful in the twenties and the thirties, began to run out of steam in the sixties. At that time, other prominent figures of analytic philosophy were much less prone to reject any form of metaphysics as fundamentally unclear or unscientific: Quine's famous criterion of ontological commitment had already been formulated in a paper which appeared in the Review of Metaphysics, Strawson had published his Individuals. An Essay in Descriptive Metaphysics, and Kripke's semantics for modal logic would soon arouse a wave of metaphysical thinking about the existence of possible worlds. Today, metaphysics is a well established and respected important part of analytic philosophy – indeed, one of its main divisions – although the style of the authors who take part in it is, to be sure, not really akin to the one Hegel or Bergson used in their writings.