NOMINALISM (from Lat. nomen, name), the name of one of the two main tendencies of medieval philosophy, the other being Realism. The controversy between nominalists and realists arose from a passage in Boéthius’ translation of Porphyry’s Introduction to the Categories of Aristotle, which propounded the problem of genera and species, (1) as to whether they subsist in themselves or only in the mind; (2) whether, if subsistent, they are corporeal or incorporeal; and (3) whether separated from sensible things or placed in them. The Realists held that universals alone have substantial reality, existing ante res; the Nominalists that universals are mere names invented to express the qualities of particular things and existing post res; while the Conceptualists, mediating between the two extremes, held that universals are concepts which exist in our minds and express real similarities in things themselves. Though a strong realist tendency is evident in the system of Erigena (9th century), the controversy was not definitely started till the 11th century: it lasted till the middle of the 12th, when the first period of scholastic philosophy ends. Under an appearance of much vain subtlety the controversy about universals involved issues of the greatest speculative and practical importance: realism represented a spiritual, nominalism an anti-spiritual, view of the world; while realism was evidently favourable, and nominalism unfavourable, to the teaching of the Church on the dogmas of the Trinity and the Eucharist. Nominalism was a doctrine of sceptics and suspected heretics, such as Berengar of Tours and Roscellinus. Even Abelard’s mediating doctrine of conceptualism (q.v.) was sufficiently near to obnoxious ideas to involve him in lifelong persecution. The principles of the great orthodox philosophers of the later scholastic period which begins in the 13th century, Albertus Magnus and Thomas Aquinas, were those of moderate realism. When nominalism was revived in the 14th century by the English Franciscan, William of Occam, it gave evidence of a new tendency in thought, a distrust of abstractions and an impulse towards direct observation and inductive research, a tendency which had its fulfilment in the scientific movement of the Renaissance. Occam’s dictum “Entia non multiplicanda sunt praeter necessitatem” was inspired by a spirit similar to that of Bacon. Though nominalism is properly a medieval theory, the tendency has passed over into modern philosophy: the term “nominalist” is often applied to thinkers of the empirical, sensationalist school, of whom J. S. Mill may be taken as the chief representative. (H. St.)