CONCRETE, a term used in various technical senses, with the general significanc of combination, conjunction, solidity. Thus the building material made up of separate substances com bined into one is known as concrete (see below). In mathematics and music, the adjective has been used as synonymous with "con tinuous" as opposed to "discrete," i.e., "separate," "discontinu ous." This antithesis is no doubt influenced by the idea that the two words derive from a common origin, whereas "discrete" is derived from the Latin discernere (to discriminate), as "concrete" is derived from concrescere (to grow together). In logic and also in common language concrete terms are those which signify per sons or things as opposed to abstract terms which signify quali ties, relations, attributes (so J. S. Mill). Thus the term "man" is concrete, while "manhood" and "humanity" are abstract, the names of the qualities implied. Confusions between abstract and concrete terms are frequent; thus the word "relation," which is strictly an abstract term implying connection between two things or persons, is often used instead of the correct term "relative" for people related to one another. Concrete terms are further sub divided as singular, the names of things regarded as individuals, and general or common, the names which a number of things bear in common in virtue of their possession of common character istics. These latter terms, though concrete in so far as they denote the persons or things which are known by them (see DENOTA TION), have also an abstract sense when viewed connotatively, i.e., as implying the quality or qualities in isolation from the indi viduals. The ascription of adjectives to the class of concrete terms, upheld by J. S. Mill, has been disputed on the ground that adjectives are applied both to concrete and to abstract terms. Hence some logicians make a separate class for adjectives, as being the names neither of things nor of qualities, and describe them as attributive terms.
See J. S. Mill, System of Logic, 1874; J . N. Keynes, Formal Logic, 1906; H. W. B. Joseph, Introduction to Logic, 1916; A. Wolf, Essentials of Logic, 1926.