CONTINGENCY. - In its generic meaning, c. is the happening "both necessary and not necessary or possible" (Aristotle, Anal. Pr., I, 3, 25 a 37). In philosophical usage it indicates the contrary of what is necessary and is therefore nearly synonymous with "possible," with "that which can be or not be," within the sphere of thought, of being, or of becoming. Waitz maintained a clear difference between "possible" and c., but the opinion defended by H. Maier (Die Syllogistik des Aristoteles, I, Tübingen 1896, p. 194) prevails — that Aristotle uses the two terms as synonyms (Anal. Pr., I, 10, 13, 15, 21; Anal. Post., I, 6, 74 b 38) and that the criteria given for the one are those given for the other (Anal. Pr., I, 13, 32 a 18; Physic., VIII, 1, 243 a 11; Met., X, 3, 1047 a 26). The only difference is that c. emphasizes more the fact that the possibility is rooted in a real "δύναμις" (cf. W. D. Ross, Aristotle's Metaphysics, II, Oxford 1928, p. 245).
In logic, propositions are called contingent in which the connection between subject and predicate is indifferent: "man is white," "Socrates walks" (Anal. Pr., I, 13, 32, a 18). In metaphysics a distinction is drawn between a c. of existing and a c. of operating; all the modalities of c. are traced back to two roots, "matter" for bodies and "freedom" for spiritual substances. If everything were necessarily determined, the mechanists and fatalists would be right, but this is not so (De Interpr., 9, 19, a 7 ff.). Since "prime matter" is pure potency, it is and remains of itself disposed to receive all bodily "forms." When therefore it is under a form, it is not bound to it forever, but remains in potency to all the other forms, under which it can in fact successively pass, when through the action of contrary qualities the body is corrupted and a new substance is generated. C. is therefore synonymous with "corruptibility": "Quod aliqua quandoque sint et quandoque non sint, habent ex materia in quantum subiectum privationi vel formae" (St. Thomas, Comm. in De Coelo et Mundo, I, lect. 29, ed. Parm., XIX, p. 75a). Hence spiritual substances, which in Thomist metaphysics are devoid of any matter, should not be called contingent but necessary (that is, immortal): "Ea vero quae ab eo sic producta sunt ut in sempiternum sint, habent potentiam et virtutem ad semper essendum et nullo modo ad hoc quod aliquando non sint" (ibid., p. 75b.; De Pot., q. 5, a. 3; C. Gant., II, 30): a doctrine that underlies the third way (Sum. Theol., 1ᵃ-2ᵃc, q. 3). The Neo-Scholastics usually adhere to the vague Wolffian meaning of c., as synonymous with that which is finite, created.
One speaks of "c. in operating" both in the corporeal order and in the spiritual one. Intelligent substances, which have as the adequate object of their operation and striving the universal Good, remain "free" in the face of particular finite goods and of means not necessary to the ultimate end. But even in the corporeal world there are contingent causes. While some effects come about of (natural) necessity because they are characteristic of a given nature, to others it is indeed inclined, but it can be impeded by the intervention of another cause; to others finally it is inclined only in remote potency and is not determined more to one than to the other except by the concurrence (concursus) of other causes, or by the occurrence of certain precise conditions that are likewise contingent (St. Thomas, Comm. in Periherm., I, lect. 13-14, ed. Parm., XVIII, p. 30 ff.). This is what is said to happen according to "chance" (in natural events) or "fortune" (in human events).
Boutroux (v.), with the aim of safeguarding human freedom, proposed a "philosophy of c." according to which in the world both of bodies and of spirits, there is no law that
is absolute necessity: "The supreme principles of things would
still be laws, but moral and aesthetic laws,
expressions more or less immediate of divine perfection"
which is pure and perfect "spontaneity" in which all creatures
participate, though in different forms and degrees (p. 169).