Logical positivism (LP) was a short-lived but highly influential movement that helped establish the field of philosophy of science during the first half of the twentieth century. This entry summarizes LP’s core proposals in their historical context. LP was a form of empiricism that differed markedly from those found in Hellenistic Dogmatism and Hume’s British empiricism. The latter led to Kantian rationalism, which attempted to give a more plausible account of the necessity, universality, and empirical relevance of mathematical knowledge. Another branch of LP’s genealogy stemmed from the nineteenth-century development of symbolic logic, culminating in early-twentieth-century logicism, which aimed to reduce mathematics to logic. This branch, plus the advent of relativistic mechanics, challenged Kantian rationalism and inspired efforts to reconcile it with the new developments. LP arose largely as an opposition to these attempts, unfolding as a proposal to restrict meaningful philosophy to mathematics and the logical analysis of scientific language while curtailing metaphysical speculation. Although LP has largely been abandoned, its pursuit of clarity, logical rigor, and empirical accountability continues to inform research in psychology and other sciences.