ACCIDENT. — Etymologically, an accident (from Lat. accidere = to happen; Gr. συμβεβηκός) is what may be said of something but not necessarily (logical sense), what inheres in something without constituting its substance (metaphysical sense). In its logical sense, the accident is distinguished not only from what constitutes the “species” (“definition”) of a thing (= genus and difference) but also from “property” (ἐνδον), that is, from what derives “necessarily” (καὶ σὰν ἀπὸ) from the essence of something. In this sense, Aristotle defines the accident as what is “indifferent” to the essence of something: ... id cui contingit inesse et non inesse uni eidemque, ut V. gr. “sedere” alicui uni (Top. I, 5, 102 b 4). The logical accident constitutes the final “predicable” (v.) in the well-known classification of Porphyry.
In its metaphysical sense, accident is opposed to substance and embraces the entire realm of being that pertains to the nine “predicaments” (καὶ σὰν ἀπὸ) following substance, indicating the secondary contents and modes of being. An accident is thus all that lacks its own ontological consistency and, in order to “exist,” must belong (“inhere”) to a substance as its real foundation or “substratum” (συσκευόμενον): it is therefore an accident, a certain secondary reality or essence, destined to integrate and develop the principal reality of the substance upon which it depends both in being and in existence. In this sense, the accident cannot be called an “ens” but rather “ens entis” and thus “cuius esse est inesse”: Nam ens dicitur quasi esse habens, hoc autem solum est substantia. Accidentia autem dicuntur entia, non quia sunt, sed quia magis ipsis aliquid est; sicut albedo dicitur esse quia eius subiectum est album. Ideo non dicuntur simpliciter entia, sed entis entia, sicut qualitas et motus. (St. Thomas Aquinas, Comm. in XII Metaph. Arist., I, 2419). Thus, the accident exists by virtue of the act of being of the substance and has as its property the “aptitudo ad subiectum,” whereby its definition is: “res cui debetur esse in alio” (St. Thomas Aquinas, In II Sent., dist. 24, q. I, a. 1, ad 2; cf. Sum. Theol., 3ª, q. 77, a. 1, ad 2). In this intrinsic order that accidents have to substance, Aristotle and St. Thomas see the possibility and unity of metaphysics as a science, insofar as the unity of being is preserved and founded. In this way, the strongly dialectical relationship between substance and accident in the sphere of finite beings is revealed, for while substance may be called the support and even the cause of accidents, accidents in turn constitute their acts and perfections: “unde et accidens forma dicitur” (St. Thomas Aquinas, Q. unica De virtutibus in communi, a. 3). It is moreover through accidents that substance acts and is acted upon, and it is through the action of accidents that generation and corruption and all becoming are “prepared,” both in the physical world and in the spiritual.
From a phenomenological standpoint — when one admits with Aristotle that our knowledge necessarily develops in dependence upon experience — the first contents of consciousness refer to the accidental aspects of reality, and essence, as such, constitutes only the final term of man’s search for the nature of things. This first phase of human knowledge, which Aristotle calls “induction” (v.), encompasses that entire sector of the assimilation of the real by the human spirit that precedes and prepares the mature processes of abstraction and reflection. For, if it is true that the “middle term” of demonstration for discovering the properties of something and its ontological foundation is the essence of the thing itself, it is no less true that for us accidents “multum conferunt ad cognoscendum quod quid est” (De anima I, 1, 402b, 21 s).
In Scholasticism, the divisions of the accident (absolute and modal, proper and common, intrinsic and extrinsic, etc.) were developed and gave rise to very complicated discussions. The doctrine of accidents is of fundamental importance for the Catholic doctrine of certain mysteries of faith (Grace, sin, sacraments: particularly the Eucharist). In modern philosophy, and already in ancient and medieval subjectivism, the problem of accidents was absorbed into that of the subjectivity of sensory qualities and the denial of the substantiality of being.