RELATION. – From referre, it signifies the ordering of one thing to a term, and its formal character consists precisely in this being toward another, which distinguishes it from the absolute categories of being. absolute (v.) and relative in fact entail various meanings: sometimes absolute means that being which does not depend on another, as is God (ens a se), in opposition to the creature, which depends on him (ens ab alio) and is therefore something relative; or substance (ens in se), in opposition to accident (ens in alio). Properly speaking, however, absolute is every reality (God-creature, substance-accident) and every principle constitutive or perfective of a substance, whereas relative, in the strict sense, signifies in itself neither substance nor perfection of substance, but formally only the order or relation of one thing to another. Hence relation, in its concept, does not even imply reality, since a relation may be merely thought or constituted by the mind (relation of reason, e.g., identity), or may exist in reality independently of our mind (real relation, e.g., paternity and filiation); and when it is real, it may be substantial (a relation subsisting in itself; V. TRINITÀ SANTISSIMA) or accidental, that is, inherent in a subject (every other real relation). Inherent or accidental real relations are also called “predicamental”: category (v.) of relation refers to them, whereas the “transcendental” relations, improperly so called, are relations existing between the constitutive principles of a being, form (v.) and, in general, act (v.) and potency, and are identified with them.
In ancient philosophy the concept of relation does not appear to have been philosophically elaborated until Aristotle, who posits relation as the fourth predicament (after substance, quantity, and quality) and clearly determines its nature (πρὸς τῷ), affirming its objective reality (Cat., 7; Met., V, 15). The real value of relation was instead denied in ancient thought by the skeptics (Sextus Empiricus, Adv. math., VIII, 463), and later by Plotinus (Enn., VI, 1, 6) and Boethius (De Trin., 6). In medieval philosophy, analysis of the concept of relation assumes particular importance because of its connections with the Trinitarian dogma. Not a few scholastics (besides the Arabs Avicenna and Averroes [v.]), such as Peter Aureolus, William of Ockham (v.), and the “nominalists,” admit only the reality of divine relations, reducing all others to relations of reason (“dico quod relatio non est fundamentum sed tantum intentio vel conceptus in anima importans plura absoluta”: Ockham, I Sent., dist. 30, q. 1). But in its principal representatives, scholastic thought, both medieval and modern, agrees in affirming the existence of real predicamental or accidental relations, in addition to the divine relations. The proof is drawn from the existence in the world of an order independent of our thought (for which reason the world was already called πένατος by the ancients): this order is a relation, or rather a complex of relations, which are themselves real, for the order itself is real. Similarly, the dependence of the effect on the cause, and of the finite and participated being on Infinite Being, is a real relation. It is true that reason alone perceives the order of the world or the dependence of the effect on the cause (the animal does not formally perceive order as such), but it does not follow that relation is necessarily brought into actuality by reason and that no real relations exist outside human thought. It is still a disputed question among scholastics whether a real predicamental relation entails a reality distinct not only from the subject and the term between which the relation obtains, but also from the foundation which causes it (e.g., generation, the foundation of the relation of paternity and filiation existing between father and son). Not a few authors, especially those of the Suarezian school (F. Suárez, Disp. Met., d. 47, s. 2), identify the relation with the foundation, while the term would be an extrinsic connotation; or they identify it with both the foundation and the term. Others, with St. Thomas (De pot., q. 7, a. 9 and passim) and Scotus (Oxon., II Sent., dist. 1, q. 4, n. 5), maintain that a real predicamental relation entails an accidental reality distinct from the subject, foundation, and term, and they deduce this from the very nature of relation, which is essentially something relative, whereas subject, foundation, and term are absolute realities. This doctrine is indicated in the sixth of the 24 Thomistic theses: “Praeter absoluta accidentia est etiam relativum sive ad aliquid. Quamva enim ad aliquid non significet secundum propriam rationem aliquid alicui inhaerens, saepe tamen causam in rebus habet et ideo realem entitatem distinctam a subiecto”.
In modern philosophy the reality of relation is again denied, and only the foundation is admitted as real; thus by Gassendi (Philos. epic. synth., II, 30, § 4), Hume (Treat. on hum. nat., I, sez. 5), and Wolff (Ontologia, § 857). For Kant, relation has no objective reality, but is a subjective a priori form according to which the intellect necessarily judges; more precisely, it is one of the four fundamental categories, comprising under itself those of substantiality, causality, and reciprocity (Kritik der rein. Vern., II, 1). Relation conceived as a subjective a priori form assumes ever greater importance in post-Kantian subjectivist philosophy, idealism (v.), which, by reducing all reality to the a priori synthesis outside of which the terms are mere abstractions, resolves reality into relation, which is the synthesis itself (O. Hamelin, Essai sur les diêm. princ. de la reprès., 2ª ed., Paris 1925, p. 2). But if the idealistic reduction of reality to relation is unacceptable, the contrary position, which denies all reality to relation, must also be rejected: between these opposing extremes, scholastic thought represents the most consistent balanced solution.