CASO. — Those rare events are attributed to chance which, although unforeseen and unforeseeable, nevertheless display a certain teleological value in their outcome. It is the “combination,” encounter, or coincidence (objective element), curious because it is “interesting” (subjective element): the peasant who, while hoeing, finds a hidden treasure; the thirsty man who is killed by bandits lying in ambush near the spring; etc.
In classical mechanicism (Anaxagoras, the atomists, Empedocles, the Stoics, the Epicureans, Strato of Lampsacus), chance is a mere name put forward to conceal man’s ignorance of causes: in nature and in human life everything proceeds with rigorous necessity, which is explained differently in the various systems (cf. Aless. di Afrod., De fato, chap. II, ed. I. Bruns, Berlin 1892).
Related in one respect to the classical conception is the modern conception of chance events, which is based on the “statistical laws” or laws of large numbers. It is established that in microphysics, microbiology, astrophysics, and social phenomena, while the individual event appears to be at the mercy of chance, it is nevertheless possible to predict the “collective phenomena,” and with greater precision the larger the number of elements on which one operates. It is nevertheless generally held (E. Borel) that this concerns purely the effects of calculation and leaves intact the question of the nature of becoming, unlike ancient fatalism or immanentism (A. Tilgher).
Aristotle introduces the theory of chance as a complement to the four causes (Phys., II, 4-6, 195 b 31 ff.; Metaph., VI, 7, 1032 a 27 and 9, 1034 b 9), because it is often confused with them, although in reality it signifies the absence of causes. Indeed, whereas natural events take place through the action of the form of an agent to which they correspond and from which they derive “necessarily and always” if the nature of the cause is necessary, or “for the most part” if the cause is defective and contingent, chance, on the other hand, is said of what occurs “per accidens,” of that which, in relation to proximate causes, displays no law: under this vague designation the most disparate events may be indicated, from simple combinations and insignificant “fortuitous” events, to deviations from the physical laws (monstrous births and the like) of the material world, to the combinations or incidents of properly human life that have changed the face of the world (Caesar’s “ales lacta est” and the sending of Lenin to Russia in the armored railway carriage...). Aristotle distinguishes simple chance (αὐτιέμετον) from fortune and misfortune (τύχη, ἀτύχη), in which its repercussions in human benefit or harm are considered, without pronouncing on whether they in some way depend on the First Cause. In Christian creationism, however, both because of the omnipotence of divine causality and because of the vastness of the consequences that these events often display, they are attributed in a special way to God, whose providence establishes, unfolds, and embraces from above the history both of individuals and of nations, with a single gaze (Sim. Theol., 1ª, q. 115, a. 6; q. 116, a. 1; In Periferum., I, lect. 14). V. DETERMINISMO; LEGGI STATISTICHE; PROBABILITÀ.