EXISTENCE. — It is the act, the fact, or the reason by which it can be said that something is, there is, and it answers the question “whether it is” (whether it has been or will be).
In the generic meaning of “reason,” existence is the belonging of the predicate to the subject in a proposition and therefore what underlies that movement of the spirit that unites (or separates) them in affirmation (or negation): existence is then understood as a simple abstract conceptual relationship proper to logic and also to pure mathematics, to the philosophy of values (cf. W. Burkamp, Begriff und Beziehung, Leipzig 1927, § 49 ff.). Its opposite is non-existence, which is the “repugnance,” or the contradiction between concepts.
Existence as fact is given by experimental verification whereby something can be indicated and individuated as a singular reality in history and experience. It is the most correct meaning of existence often used in the concrete form (the existent, existents) alongside the characteristics of individuality (circumstances, facts, situations...) of something or someone on which the right to claim, accuse, or defend can be founded. Its opposite is non-existence as “possibility” not yet realized.
To this sense of “realization of the possible” most traditional philosophies adhered, though not all conceived it in the same way. Thus, for some it is real singularity in opposition to abstract essence; for others it is the contingent reality of the creature insofar as it expresses a relation to divine causality; for others still it is a modification of singular essence whereby this is drawn “outside” of possibility; “assistence,” an etymology revived by the existentialists. And as these latter now do (cf. M. Heidegger, Sein und Zeit, 5th ed., Halle on the Saale 1942, § 9, p. 42 ff.), a distinction was made between esse existentiae and esse essentiae (F. Suárez, Disputationes, disp. 31, sect. VI), a distinction that further complicated the medieval controversy over the distinction between essence and existence.
In the highest sense, “essence” is the “act of being” of singular individual essence; it is therefore a participation in divine actuality received in essence with the real composition of form as act and potency (C. Gent., II, 52-54). Existence as fact, as realization in experience or history, is a result, a phenomenological consequence of such an ontological union. Hence, for St. Thomas, esse is what is most profound in every thing: “‘Esse’ is that which is most intimate and most profound in each thing, since it is formal with respect to all that is in a thing” (S. Th., I, q. 8, a. 1).
Modern philosophy seems to have remained unaware of the Thomistic notion. Fundamental for later philosophy is the Leibnizian notion, which takes existence as the mode or position of the thing: “Existence is conceived by us as a thing having nothing in common with essence, which nevertheless cannot be, because there must be more in the concept of the existent than of the non-existent, or existence must be a perfection; since in reality nothing else is explicable in existence than that it enters into the most perfect series of things; thus we conceive position in the same way as something extrinsic, which adds nothing to the thing posited, yet adds the mode by which it is affected by other things” (L. Couturat, Opuscules et fragmenta de Leibnitz, Paris 1903, p. 9). To this “extrinsicist” notion is close the notion of existence held by Kant in the precritical period. Existence is what in a thing cannot be reduced to concept, to an element of essence, and therefore “what can never be a predicate.” Existence is “the absolute position of a thing”; and for Kant, who here unconsciously approaches the Thomistic position, existence is what ultimately grounds possibility so that “the intrinsic possibility of things presupposes some existence” (Der einzig mögliche Beweisgrund zu einer Demonstration der Existenz Gottes, in Kleine Schriften, Italian trans. by P. Carabellese, Bari 1928, p. 44). A thoroughly realistic notion to which Kant remained faithful, as evidenced by the example of the 100 thalers in his critique of the ontological argument: Kant’s defect was to have been satisfied with this crude positivity without investigating further the relations between essence and existence, which led him to brand even St. Thomas’s a posteriori proofs of the existence of God as ontological arguments.
The distinction between logical and ontological order, which was nonetheless preserved in dualist philosophies, disappears in the rationalist monism of Spinoza first and then Hegel. For Spinoza, existence is a predicate of the sole “Substance” to which it belongs as a necessary requirement (Ethics, Part I, prop. VII). In Hegelian philosophy, existence and reality were separated; existence is the particular, the external phenomenon that is real only insofar as it is taken up into the Idea, as an element of the whole that is Spirit in the development of its history (Science of Logic, II, sect. 2, ch. 1). The “quid” for Hegel characterizes the “appearance” of essence; it is the immediate existence that arises from essence, whereby in existence the “undistinguished unity” of essence with its immediacy is realized.
In contemporary philosophy, various currents of thought that qualify as “philosophy of existence” (v. esp. EXISTENTIALISM) have made existence the cornerstone of opposition to dialectical pantheistic monism; existence is understood here as the primary reality of the single “person” isolated in its own situation in the world and engaged in its tasks: “ex-sistere,” that is, stepping out through the act of personal decision.