The mention of this last sort of incommunicability would be superfluous, and indeed unintelligible, did we not know from Divine Revelation that the human nature of our Divine Lord and Saviour, Jesus Christ, though it is a complete and most perfect individual nature, is nevertheless not a person, because It is assumed into the Personality of the Second Person of the Divine Trinity, and, united hypostatically or personally with this Divine Person, subsists by virtue of the Divine Subsistence of the latter.
We see, therefore, what subsistence does for a complete individual nature in the static order. It makes this nature sui juris, incommunicable, and entirely independent in the mode of its actual being: leaving untouched, of course, the essential dependence of the created “subsisting thing” or “person” on the Creator. In the dynamic order, the order of activity and development, subsistence makes the complete individual nature not only the ultimate principle by which all the functions of the individual are discharged, but also the ultimate principle or agent which exercises these functions: while the nature as such is the ultimate principium quo, the nature as subsisting is the ultimate principium quod, in regard to all actions emanating from this nature. Hence the scholastic aphorism: Actiones sunt suppositorum. That is, all actions emanating from a complete individual nature are always ascribed and attributed to the latter as subsisting, to the “subsisting thing” or “person”. In regard to an individual human person, for instance, whether his intellect thinks, or his will resolves, or his imagination pictures things, or his eyes see, or his hand writes, or his stomach digests, or his lungs breathe, or his head aches, it is the man, the person, properly, that discharges or suffers all these functions, though by means of different faculties, organs and members; and it is to him properly that we ascribe all of them.[287]
Now the individual human person is neither his soul, nor his body, nor even both conceived as two; he is one being, one complete substance or nature composed partly of a spiritual principle or soul and partly of a material principle which the soul “informs” and so constitutes a living human body. Hence the human soul itself, whether we consider it as united to the material principle in the living human person, or as disembodied and separate from its connatural material principle, is not a complete substance, is not capable of subsisting and having its human activities referred ultimately to itself as the subsisting, personal principle which elicits these activities. No doubt the disembodied soul has actual existence, but it has not the perfection of subsistence or personality: it is not a complete individual of the human species to which it belongs, and therefore it cannot be properly called a human person, a complete subsisting individual of the human species.[288]
Furthermore, even though an individual nature be complete as a nature, endowed with all the substantial and specific perfections which constitute it a complete individual of the species to which it belongs, nevertheless if it is assumed into the personality of another and higher nature, and subsists in personal union with the latter and by virtue of the latter's subsistence, then that nature, not having its own proper and connatural subsistence, is not itself a person. Nor can the actions which are elicited by means of it be ascribed ultimately to it; they must be ascribed to the person by whose subsistence it subsists and into whose personality it has been assumed. If an individual human nature be thus hypostatically or personally assumed into, and united with, a higher Divine Personality, and subsists only by this Personality, such a human nature will be really and truly an individual nature of the human species; the actions elicited through it and performed by means of it will be really and truly human actions; but it will not be a human person; while its actions will be really and truly the actions of the Divine Person, and will therefore be also really and truly divine: they will be the actions of the God-Man, divine and human, theandric. All this we know only from Divine Revelation concerning the hypostatic union of the human nature of Christ with the Person of the Divine Word; nor could we know it otherwise. But all this does not modify, it only supplements and completes, what the light of reason discloses to us regarding the subsistence or personality of any complete individual nature.
We are now in a position to give nominal definitions of subsistence and personality both in the abstract and in the concrete, i.e. definitions which will indicate to us what exactly it is that these terms denote,[289] and which will thus enable us to inquire into their connotation, or in other words to ask what is it precisely that constitutes subsistence or personality.
By “subsistence” (“subsistentia,” “suppositalitas”) we mean that perfection whereby a fully complete individual nature is rendered in every way, in its being and in its actions, distinct from and incommunicable to any and every other being, so that it exists and acts sui juris, autonomously, independently of every other being save the Creator.[290]
By a “subsisting being” in the concrete (ὑπόστασις, “suppositum,” hypostasis), we mean a being endowed with this perfection of subsistence; in other words, a being that is a complete individual nature existing and acting in every way distinct from and incommunicable to any other being, so that it exists and acts sui juris, autonomously.
“Personality” is simply the subsistence of a complete individual nature that is rational, intelligent.
A “person” is simply a subsisting nature that is rational, intelligent: Persona est suppositum rationale. The definition given by Boëtius is classic: “Persona est substantia individua Rationalis naturae”: “the individual substance of a rational nature,”—where the term individual is understood to imply actually existing and subsisting.
The special name which has thus been traditionally applied to rational or intelligent subsisting beings (as distinct from animals, plants, and material “things”)—the term “person” (“persona,” a mask: per-sonus; cf. Gr. προσωπέιον, from προσώπον, the face, countenance)—originally meaning a rôle or character in a drama, came to be applied to the subsisting human individual, and to connote a certain dignity of the latter as compared with the lower or non-rational beings of the universe. And in fact the ascription of its actions to the subsisting being is more deeply grounded in the subsistence of rational, intelligent [pg 266] beings, who, as free agents, can more properly direct and control these actions.[291]