THE philosophical school of thought called Logical Positivism began officially with the "scientific program" of the Vienna Circle presented to Moritz Schlick in 1929 when he returned to Vienna from an academic visit to the United States. The actual beginning can be traced, however, to the publication of Ludwig Wittgenstein's Tractatus Logico-Philosophicus in 1921. Logical Positivism constitutes an attempt to elucidate the empirical point of view by means of modern developments in logic. As a fusion of two distinct streams of thought it is best understood in its historical setting and development.
Speaking very generally, the principal ancestor of positivism was David Hume. His contention that no matter of fact can be established by merely logical means and that, consequently, causal relations of distinct events can be discovered only by experience, is a fundamental insight with which all logical positivists will agree. But positivists are further indebted to Hume for the doctrines that the ultimate meaning of words is determined by concrete and simple data of experience, and that logical deductive connections encountered in the formal sciences (logic and pure mathematics) depend on definitions of terms. However, Hume and his successors in the British empirical tradition argued their case in ways which could not and did not withstand the Idealists' criticism. For Hume's philosophy, even if it did not confuse psychological with logical questions, was frequently stated in language which seemed to justify such an attack. As the empirical school developed, it became clear that it could not provide an adequate account of logic either in the Aristotelian-Scholastic sense of the word or in the sense it had acquired from the Hegelian Idealists.
The contributions of philosophers and mathematicians who were either unaffected by debates among Empiricists, Materialists, and Idealists, or who worked in conscious opposition to all these tendencies must now be considered. Partly as a survival of the Aristotelian-Scholastic traditions in logical theory, and more espe-