In scholastic philosophy and theology, incommunicability is that property which, together with subsis tence, characterizes the person and, less properly, the irrational supposit; it indicates the person's individuality, distinctness, and independence.
Historical Aspects. The Vulgate of Wis 14.21 used incommunicabile nomen to designate what is the prerogative of God alone (cf. St. Augustine, In evang. Ioh. 79.2; Corpus Christianorum. Series latina 36:527). Boethius used incommunicabilis proprietas or qualitas of what is proper to a single individual (Herm. sec. 2; Patrologia Latina, ed. J. P. Migne (Paris 1878–90) 64:462–64; ed. C. Meiser, Lipsiae, 1877–80, 137–41). Fulgentius of Ruspe came closer to medieval speculations on personality when he said of the Trinity: "…se illa una veraque divinitas in singulis personis voluit incommunicabiliter nominari …" (Epist. 14.8; Patrologia Latina 65:399). But it was not till the Middle Ages that incommunicabilitas was used more technically and frequently for what is characteristic of the person. Boethius's definition of person as naturae rationalis individua substantia (C. Eut. 3, ed. H. Stewart and E. Rand, 84) was the basic point of departure. Richard of Saint-Victor sought to replace this formula as applied to God with naturae divinae incommunicabilis exsistentia (De Trinitate 4.21–24; ed. G. Salet, Sources Chrétiennes, ed. H. de Lubac et al. (Paris 1941–) 63:278–86; cf. pp. 487–89). Boethius's formula survived, however, although today it yields primacy to distinctum subsistens in natura intellectuali (St. Thomas, In 1 sent. 23.1.4). While incommunicabilitas did not appear in these two classic definitions, it was commonly used in their analysis, as the equivalent or refinement of individua and distinctum. In Alexander of Hales (Summa theologiae 3a; Quaracchi 4.2:78–79), followed by St. Bonaventure (In 3 sent. 5.2.2 ad 1; Quaracchi 3:133b), incommunicabilitas designated only one of three aspects of the individuality proper to the person. Such was not the case in St. Thomas's usage, which designated all three aspects as incommunicabilitas (In 3 sent. 5.2.1 ad 2); this usage has subsequently prevailed (see below).
Analysis. Each existent (ens simpliciter ) as a unity is "undivided in itself, divided from every other." What this classic description seeks to convey is that every being as one: (1) is a totality, identical with itself, completely constituted in itself, an individual; and (2) precisely as such stands over against every other being. "Undivided in itself" regards the being's self-referent aspect, its self-identity, totality, completeness; "divided from every other" situates the being in the universe of distinct existents. The notion of supposit is a more technical designation of existent being in its unity. In the definition of the supposit as the distinct or incommunicable subsistent, subsistence represents the self-referent aspect of the supposit, while incommunicability represents its other-referent aspect. Following St. Thomas, scholastics speak of a threefold commonness or indistinctness as excluded from the supposit as incommunicable: (1) the commonness of a universal (for the supposit is subsistent, individual) or quasiuniversal (to allow for the commonness had by the divine nature in the trinity); (2) the commonness of a part (for the supposit is complete); (3) the commonness had by "assumption" by another supposit, as in the incarnation (see below). Incommunicability does not, however, exclude that the Divine Person of the Son draw His human nature to share in His divine subsistence.
Applications. (1) Irrational supposits possess incommunicability only by a very extended analogy, since their self-identity is minimal. (2) The human (and angelic) person, constituted as such because of its intellectuality and freedom exercised by a created ultimate subject of existence, is characterized by a lofty, though still imperfect, self-possession, and hence by incommunicability. The moral and juridical sacredness of the person has its roots in this ontological inviolability; it is because the person exists in itself and for itself that it cannot be treated as a mere means. (3) In the unique instance of the humanity of Christ, an individual created nature, rational and free, is not the ultimate subject of incommunicable existence; rather the word, divinely incommunicable from eternity, is now, in this individual assumed nature, humanly incommunicable. How a reality fully individual as nature can lack the individuality or incommunicability proper to person is the essential problem arising from the mystery of the Incarnation (see jesus christ in theolo gy). (4) In the Trinity the divine nature, though subsistent, lacks strict incommunicability because of being common to the three Persons; the same is true of the subsistent relation of active spiration, common to Father and Son. It is rather in the three Divine Persons, each a distinct, subsistent relation, that one finds the strict incommunicability of which there is question here (see re lations, trinitarian). From the Christological and Trinitarian applications it is clear that the philosophical analysis of incommunicability is strongly dependent on the two central Christian mysteries; it is doubtful, at the very least, that unaided reason would have perceived any distinction between the singularity or individuality of an existing nature and the further individuality or incommunicability that specifies the person.
Incommunicability and Personal Communication. Modern personalist and existentialist philosophy emphasizes interpersonal communication as essential to the person (see personalism; existentialism); man attains self-realization only in meaningful encounter with the other. Superficially this notion might seem to conflict with the notion of the person as incommunicable. In fact the two notions are not only compatible but require one another. Only as unique, distinct, and incommunicable can the person enter into a communion that is not a depersonalizing self-abdication; only as open to communion can the person retain a self-possession that is not solipsistic. The Trinitarian mystery, where each incommunicable Person is constituted by a distinct, subsistent relation, is for the Christian the model and guarantee of this necessary complementarity.
See Also: assumptus-homo theology; consubstantiality; created actuation by uncreated act; homoousios; hypostasis; kenosis; person, divine.
Bibliography: l. de raeymaeker, The Philosophy of Being, tr. e. h. ziegelmeyer (St. Louis 1954) 240–47. l. billot, De Verbo Incarnato (9th ed. Rome 1949) 61–78; De Deo uno et trino (7th ed. Rome 1935) 460–74. a. michel, Dictionnaire de théologie catholique, ed. a. vacant et al., 15 v. (Paris 1903–50) 7.1:407–29.
[t. e. clarke]