Accident [Lat. accidere, to happen—what happens to be in a subject; any contingent, or non-essential attribute].
I.—The obvious division of things into the stable and the unstable, the more or less independently subsistent and the dependent, or essentially inherent, appears beset with obscurity and difficulty as soon as it is brought under reflective consideration. In their endeavor to solve the problem, philosophers have followed two extreme tendencies. Some have denied the objectivity of the substantial or noumenal element, and attributed it wholly or in part to the mind; others have made the phenomenal or accidental element subjective, and accorded objectivity to substance alone. These two extreme tendencies are represented among the ancient Greek materialists and atomists on the one hand and the Eleatic pantheists on the other. Aristotle and his medieval followers steer a middle course. They hold to the objectivity both of substance and of accident, though they recognize the subjective factor in the mode of perception. They use the term accident to designate any contingent (i.e. non-essential) relation between an attribute and its subject. As such it is a merely logical denomination, one of the five "predicables" or universals, modes of systematic classification—genus, difference, species, property, accident. In this sense it is called predicable, as distinguished from predicamental, accident, the latter term standing for a real objective form or status of things, and denoting a being whose essential nature it is to inhere in another as in a subject. Accident thus implies inexistence in substance—i.e. not as the contained in the container, not as part in the whole, not as a being in time or place, not as effect in cause, not as the known in the knower; but as an inherent entity or mode in a subject which it determines. Accidents modify or denominate their subject in various ways, and to these correspond the nine "Categories": (I) quantity, in virtue whereof material substance has integrant, positional parts, divisibility, location, impenetrability, etc.; (2) quality, which modifies substance immediately and intrinsically, either statically or dynamically, and includes such inherents of substance as habit, faculty, sense-stimuli, and figure or shape; (3) relation, the bearing of one substance on another (e.g. paternity). These three groups are called intrinsic accidents, to distinguish them from the remaining six groups—action, passion, location, duration, position, habiliment— which, as their names sufficiently suggest, are simply extrinsic denominations accruing to a substance because of its bearings on some other substance. Quantity and quality, and, in a restricted sense relation are said to be absolute accidents, because they are held to superadd some special form of being to the substance wherein they reside. For this reason a real, and not a merely conceptual, distinction between them and their subject is maintained. Arguments for the physical reality of this distinction are drawn from experience; (a) internal-consciousness attesting that the permanent, substantial self is subject to constantly-shifting accidental states—and (b) external experience, which witnesses to a like permanence of things beneath the incessantly varying phenomena of nature. The supernatural order also furnishes an argument in the theology of the infused virtues which are habits supervening on, and hence really distinct from, the substance of the natural mind.
II.—With the reaction against scholasticism, led on by Descartes, a new theory of the accident is devised, or rather the two extreme views of the Greeks referred to above are revived. Descartes, making quantity the very essence of matter, and thought the essence of spirit, denies all real distinction between substance and accident. While teaching an extreme dualism in psychology, his definition of substance, as independent being, gave occasion to Spinoza's monism, and accidents became still more deeply buried in substance. On the other hand, substance seems at last to disappear with Locke, the world is resolved into a congeries of qualities (primary, or extension, and secondary, or sensible properties). The primary qualities, however, still retain a foundation in the objective order, but with Berkeley they become entirely subjectified; only the soul is allowed a substantial element as the support of psychical accidents. This element is likewise dissolved in the philosophy of Hume and the Associationists. Kant considered accidents to be simply subjective categories of sense and intellect, forms according to which the mind apprehends and judges of things—which things are, and must remain, unknowable. Spencer retains Kant's unknowable noumenon but admits phenomena to be its objective aspects or modifications.
III.—Several other classifications of accidents are found in the pertinent treatises. It should be noted that while accidents by inhesion modify substance, they are witnesses to its nature, being the medium whereby the mind, through a process of abstraction and inference, builds its analogical concepts of the constitution of substances. From this point of view material accidents are classed as (a) proper sensibles—the excitants of the individual senses, color for sight, sound for hearing, etc.—and (b) common sensibles— extension and its modes, size, distance, etc.—which stimulate two or more senses, especially touch and sight. Through these two groups of accidents, and concomitantly with their perception, the underlying subject is apperceived. Substance in its concrete existence, not in its abstract essence, is said to be an accidental object of sense.
IV.—The modern views of accident, so far as they accord to it any objectivity, are based on the physical theory that all, at least material, phenomena (light, color, heat, sound, etc.) are simply varying forms of motion. In part, the kinetic element in such phenomena was known to Aristotle and the Scholastics (cf. St. Thomas, "De Anima", III, Lect. ii); but it is only in recent times that physical experimentation has thrown light on the correlation of material phenomena as conditioned by degrees of motion. While all Neo-Scholastic philosophers maintain that motion alone will not explain the objectivity of extension, some (e.g. Gutberlet) admit that it accounts for the sensible qualities (color, sound, etc.). Haan (Philos. Nat.) frees the theory of motion from an extreme idealism, but holds that the theory of the real, formal objectivity of those qualities affords a more satisfactory explanation of sense-perception. The majority of Neo-Scholastic writers favor this latter view. (Pesch, Phil. Nat.)
V.—The teaching of Catholic philosophy on the distinct reality of certain absolute, not purely modal, accidents was occasioned by the doctrine of the Real Presence of the Body and Blood of Christ in the Eucharist, though the arguments for the theory are deduced from natural experience. The same doctrine, however, suggests the further question, whether such accidents may not be separable from substance. Reason alone offers no positive arguments for such separability. The most it can do is to show that separability involves no inherent contradiction, and hence no absolute impossibility; the Omnipotence that endows substance with the power of supporting accidents can, it is claimed, supply some other means of support. Nor would the accidents thus separated, and supernaturally supported, lose their character as accidents, since they would still retain their essential property, i.e. natural exigence of inhesion. Of course the intrinsic possibility of such separation depends solely on the supernatural interference of God, nor may it extend to all classes of accidents. Thus, e.g., it is absolutely impossible for vital faculties, or acts, to exist outside their natural subjects, or principles. Theorists who, like the Cartesians, deny the objective, distinct entity of all accidents have been obliged to reconcile this negation with their belief in the Real Presence by maintaining that the species, or accidents, of bread and wine do not really remain in the Eucharist, but that after Consecration God produces on our senses the impressions corresponding to the natural phenomena. This theory obviously demands a seemingly unnecessary multiplication of miracles and has at present few if any serious advocates. (See Eucharist.)