This book is a radical reappraisal of positivism as a major movement in philosophy, science and culture. In examining positivist movement and its contemporary impact, I had the following goals. First, to provide a more precise and systematic definition of the notion of positivism. Second, to describe positivism as a trend of thought concerned not only with the theory of knowledge and philosophy of science, but also with problems of ethics, social, and political philosophy, and show that its representatives usually thought that the problems of the latter cannot be solved without solving the former first. Third, to examine the development of positivism as a movement which preserves a certain tradition and hence possesses some coherence, although the forms of this movement changed in different historical circumstances: it was born in the eighteenth century during the Enlightenment, took the form of social positivism in the nineteenth century, was transformed at the turn of the twentieth century with the emergence of empirio-criticism, and became logical positivism (or logical empiricism) in the twentieth century. Fourth, to reveal the external and internal factors of this evolution. Fifth, to disclose the relation of positivism to other trends of philosophy. Sixth, to determine the influence the positive mind had not only upon philosophy, but upon other cultural phenomena, such as the natural and social sciences, law, politics, arts, religion, and everyday life.