The sciences do not try to explain, they hardly even try to interpret, they mainly make models. By a model is meant a mathematical construct which, with the addition of certain verbal interpretations, describes observed phenomena. The justification of such a mathematical construct is solely and precisely that it is expected to work.“Method in the Physical Sciences”, in The Unity of Knowledge (1955), ed. L. G. Leary (Doubleday & Co., New York), p. 157