EPISTEMOLOGY, in philosophy, a term applied, prob ably first by J. F. Ferrier, to that department of thought whose subject matter is the nature and validity of knowledge (Gr. E7rco'Triµ7, knowledge, and X6yos, theory, account ; Ger. Er kenntnistheorie). It is thus contrasted with metaphysics, which considers the nature of reality, and with psychology, which deals with the objective part of cognition, and, as Prof. James Ward said, "is essentially genetic in its method." Epistemology is con cerned rather with the possibility of knowledge in the abstract. In the evolution of thought epistemological inquiry succeeded the speculations of the early thinkers, who concerned themselves primarily with attempts to explain existence. The differences of opinion which arose on this problem naturally led to the inquiry as to whether any universally valid statement was possible. The Sophists and the Sceptics, Plato and Aristotle, the Stoics and the Epicureans took up the question, and from the time of Locke and Kant it has been prominent in modern philosophy. It is extremely difficult, if not impossible, to draw a hard and fast line between epistemology and other branches of philosophy. If, for example, philosophy is divided into the theory of knowing and the theory of being, it is impossible entirely to separate the latter (Ontology) from the analysis of knowledge (Epistemology), so close is the connection between the two. Again, the relation between logic in its widest sense and the theory of knowledge is extremely close. Some thinkers have identified the two, while others regard Epistemology as a subdivision of logic ; others de marcate their relative spheres by confining logic to the science of the laws of thought, i.e., to formal logic. An attempt has been made by some philosophers to substitute "Gnosiology" (Gr. yvWacs) for "Epistemology" as a special term for that part of Epistemology which is confined to "systematic analysis of the conceptions employed by ordinary and scientific thought in inter preting the world, and including an investigation of the art of knowledge, or the nature of knowledge as such." "Epistemology" would thus be reserved for the broad questions of "the origin, nature and limits of knowledge" (Baldwin's Dict. of Philos. i.
PP. 333 and 414). The term Gnosiology has not, however, come into general use. (See PHILOSOPHY; KNOWLEDGE, THEORY OF.)