RELATION. — To be related, it signifies the rapport of one thing to a term, and its formal character consists precisely in this being to another, which distinguishes it from the absolute categories of being. The terms absolute (v.) and relative in truth carry various meanings, for sometimes by absolute is understood that being which does not depend on others, such as God (ens a se) in opposition to the creature which depends on Him (ens ab alio) and is therefore something relative; or else substance (ens in se) in opposition to accident (ens in alio). But properly speaking, absolute is every reality (God-creature, substance-accident) and principle, whether constitutive or perfective, of a substance, while relative in the strict sense does not in itself signify either substance or perfection of substance, but formally only the order or rapport of one thing to another. Therefore, relation in its concept does not even imply reality, since the relation can be only thought or constituted by the mind (relation of reason, e.g., identity), or else exist in reality independently of our mind (real relation, e.g., paternity and filiation); and when it is real it can be substantial (relation subsisting in itself; V. TRINITY, HOLY) or accidental, i.e., inhering in a subject (every other real relation). Real relations that are inhering or accidental are also called “predicamental” because the predicament or category (v.) of relation refers to them, while the “transcendental,” improperly so called, relations are rapports existing between the constitutive principles of an entity, such as matter and form (v.) and in general act (v.) and potency, with which they are identified.
In ancient philosophy the concept of relation does not appear philosophically elaborated until Aristotle, who places relation as the fourth predicament (after substance, quantity, and quality) and clearly determines its nature (πρὸς τὰ) affirming its objective reality (Cat., 7; Met., V, 15). The real value of relation was, however, in ancient thought, denied by the sceptics (Sextus Empiricus, Adv. math., VIII, 463) and later by Plotinus (Enn., VI, 1, 6) and Boethius (De Trin., 6). In medieval philosophy the analysis of the concept of relation assumes particular importance in relation to the dogma of the Trinity. Not a few scholastics (in addition to the Arabs Avicenna and Averroes [v.], such as Peter Auriol, William of Ockham [v.], and the nominalists) admit only the reality of divine relations, reducing the 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, both medieval and modern, scholastic thought is in agreement in affirming the existence of real predicamental or accidental relations, in addition to divine relations. The proof is drawn from the existence, in the world, of an order independent of our thought (for which already by the ancients the world was called χάρις); such an order is a relation or rather a complex of relations that are themselves real if the order is real. Similarly, the dependence of the effect on the cause, of the finite and participated being on the Infinite Being, is a real relation. It is true that only reason perceives the order of the world or the dependence of the effect on the cause (the animal does not formally perceive the order as such), but it does not follow that the relation is necessarily posited in act by reason and that real relations do not exist outside human thought. It is still a debated question among scholastics whether a real predicamental relation implies a reality distinct, besides the subject and the term between which the relation holds, also from the foundation which is the cause (e.g., generation, foundation of the relation of paternity and filiation existing between father and son). Not a few authors, especially 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 else identify it with the foundation and the term. Others, with St. Thomas (De pot., q. 7, a. 9 and passim) and with Scotus (Oxon., II Sent., dist. 1, q. 4, n. 5), maintain that a real predicamental relation implies 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, while subject, foundation, and term are absolute realities. This doctrine is indicated in the sixth of the 24 Thomistic theses: “Pracere absoluta accidentia est etiam relativum sive ad aliquid. Quamvis 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 Gassendi (Philos. epic. synth., II, 30, § 4), Hume (Treat. on hum. nat., I, sec. 5), Wolff (Ontologia, § 857). For Kant, relation has no objective reality, but is a subjective a priori form according to which the intellect necessarily judges, and precisely it is one of the four fundamental categories, which comprehends under itself those of substantiality, causality, and reciprocity (Kritik der rein. Vern., II, 1). The concept of relation as a subjective a priori form assumes ever greater importance in post-Kantian subjectivistic philosophy, especially in absolute idealism (v.), which, reducing all reality to the a priori synthesis, outside of which the terms are pure abstractions, resolves reality into relation, which is the synthesis itself (O. Hamelin, Essai sur les éléments. prin. de la repres. 2ª ed., Paris 1925, p. 2). But if the idealistic reduction of reality to relation is unacceptable, so too must be rejected the contrary position that denies all reality to relation: between the opposing extremes, scholastic thought represents the most consistent solution of equilibrium.