If there is a movement or school that epitomized or typified analytic philosophy in the middle of the twentieth century, it was, by all odds, logical empiricism. Logical empiricists such as Hans Reichenbach, Rudolf Carnap, Carl G. Hempel, and Herbert Feigl had, by 1950, influenced the major fields of analytic philosophy. They had been instrumental in creating a scientifically and technically informed philosophy of science, in establishing mathematical logic as a topic in and a tool for philosophy, and in creating the project of formal semantics. Logical empiricism provided an importantly new understanding of the nature of empiricism and a new rejection of metaphysics. Accounts of analytic philosophy written in the middle of the twentieth century give logical empiricism a central place in the project, often repeating for analytic philosophy the revolutionary rhetoric of early logical empiricism. Because of this importance of logical empiricism in establishing the project of analytic philosophy, philosophical innovations both within and outside the analytic tradition in the 1960s and 1970s often were at pains to distance themselves from one aspect or another of logical empiricism.