Positivism is the view that the only way to obtain knowledge of the world is by means of sense perception and introspection and the methods of the empirical sciences. Positivists believe that it is futile to attempt to deduce or demonstrate truths about the world from alleged self-evident premisses that are not based primarily on sense perception. They consider, on the contrary, that knowledge of things can only be advanced by framing hypotheses, testing them by observation and experiment, and reshaping them in the light of what these reveal. Thus they regard metaphysics, in so far as it is the effort to find out about the world by methods other than those employed in the empirical sciences, as a hopelessly misdirected activity. The method of hypothesis, they hold, is applicable to any field of factual enquiry, although they admit that differences of subject-matter may call for very considerable variations of emphasis. Such variations, however, important though they be, are, on their view, matters of detail, and do not detract from the essential sameness of the effective method. This method was first consciously analysed by reference to the sciences of nature, where its use has led to impressive results both in the theoretical and practical sphere.
1 Based on a public lecture given in the University of Chicago in August, 1949. I hope I have profited from discussion both at and after the lecture.