We may add this consideration: The concept of an accident really distinct from its substance involves no intrinsic repugnance. Yet an accident is a mode of being which is so weak and wanting in reality, if we may speak in such terms, that it cannot naturally exist except by inhering, mediately or immediately, in the stronger and more real mode of being which is substance. But an incomplete substance is a higher grade of reality than any accident. Therefore if accidents can be real, _a fortiori_ incomplete substances can be real.
71. SUBSTANCE AND NATURE.-We have already pointed out (13) that the terms "essence," "substance," and "nature" denote what is really the same thing, regarded under different aspects. The term "essence" is somewhat wider than "substance," inasmuch as it means "what a thing is," whether the thing be a substance, an accident, or a concrete existing individual including substance and accidents.
The traditional meaning of the term "nature" in Aristotelian and scholastic philosophy is unmistakable. It means the essence or substance of an individual person or thing, regarded as _the fundamental principle of the latter"s activities_. Every finite individual comes into existence incomplete, having no doubt its _essential_ perfections and properties _actually_, but its _intermediate_ and _final_ perfections only _potentially_ (47). These it realizes gradually, through the exercise of its connatural activities. Every being is essentially intended for activity of some sort: "Omne ens est propter suam operationem," says St.
Thomas. And by the constant interplay of their activities these beings realize and sustain the universal order which makes the world a _cosmos_.
There is in all things an immanent purpose or finality which enables us to speak of the whole system which they form as "Universal _Nature_".(281)
Therefore what we call a _substance_ or _essence_ from the _static_ point of view we call a _nature_ when we consider it from the _dynamic_ standpoint, or as an agent.(282) No doubt the forces, faculties and powers, the active and pa.s.sive accidental principles, whereby such an agent exerts and undergoes action, are the _proximate_ principles of all this action and change, but the _remote_ and fundamental principle of the latter is the essence or substance of the agent itself, in other words its _nature_.
Not all modern scholastics, however, are willing thus to identify nature with substance. We have no intuitive insight into what any real essence or substance is; our knowledge of it is discursive, derived by inference from the phenomena, the operations, the conduct of things, in accordance with the principle, _Operari sequitur esse_. Moreover, the actually existing, concrete individual-a man, for instance-has a great variety of activities, spiritual, sentient, vegetative, and inorganic; he has, moreover, in the const.i.tution of his body a variety of distinct organs and members; he a.s.similates into his body a variety of inorganic substances; the tissues of his body _appear_ to be different _in kind_; the vital functions which subserve nutrition, growth and reproduction are at least a.n.a.logous to mechanical, physical and chemical changes, if indeed they are not really and simply such; it may be, therefore, that the _ultimate material_ const.i.tuents of his body remain _substantially unaltered_ in their pa.s.sage into, and through, and out of the cycle of his vegetative life; that they retain their elemental _substantial forms_ while they a.s.sume a _new nature_ by becoming parts of the one organic whole, whose higher directive principle dominates and co-ordinates all their various energies.(283) If this be so there is in the same individual a multiplicity of really and actually distinct substances; each of these, moreover, has its own existence proportionate to its essence, since the existence of a created reality is not really distinct from its essence; nor is there any reason for saying that any of these substances is incomplete; what we have a right to say is that no one of them separately is a complete _nature_, that each being an _incomplete nature_ unites with all the others to form one _complete nature_: inasmuch as no one of them separately is an adequate intrinsic principle of all the functions which it can discharge, and is naturally destined to discharge, by its natural union with the others, whereas there results from their union a _new fundamental principle_ of a co-ordinated and harmonized system of operations-in a word, a _new nature_.
This line of thought implies among other things (_a_) the view that whereas there is no ground for admitting the existence of _incomplete substances_, there is ground for distinguishing between _complete and incomplete natures_; (_b_) the view that from the union or conjunction of an actual multiplicity of substances, each remaining unaltered and persisting in its existence actually distinct from the others, there _can_ arise one single complete nature-a nature which will be _one being_ simply and really, _unum ens per se et simpliciter_, and not merely an aggregate of beings or an accidental unity, _unum per accidens_,-and there _does_ arise such a nature whenever the component substances not merely co-operate to discharge certain functions which none of them could discharge separately (which indeed is true of an accidental union, as of two horses drawing a load which neither could draw by itself), but when they unite in a more permanent and intimate way according to what we call "natural laws" or "laws of nature," so as to form a new fundamental principle of such functions.(284) These views undoubtedly owe their origin to the belief that certain facts brought to light by the physical and biological sciences in modern times afford strong evidence that the elementary material const.i.tuents of bodies, whether inorganic or living, remain _substantially unaltered_ while combining to form the mult.i.tudinous _natural kinds_ or _natures_ of those living or non-living material things. It was to reconcile this supposed _plurality_ of _actually distinct_ and _diverse_ substances in the individual with the indubitable _real unity_ of the latter, that these philosophers distinguished between substance and nature. But it is not clear that the facts alleged afford any such evidence. Of course if the philosopher approaches the consideration of it with what we may call the atomic preconception of material substances as permanent, unchangeable ent.i.ties, this view will preclude all recognition of _substantial_ change in the universe; it will therefore force him to conclude that each individual, composite agent has a unity which must be _less_ than substantial, and which, because he feels it to be _more_ than a mere accidental or artificial unity, he will describe as _natural_, as a union to form _one nature_. But if he approach the evidence in question with the view that substantial change is possible, this view, involving the recognition of incomplete substances as real, will remove all necessity for distinguishing between substance and nature, and will enable him to conclude that however various and manifold be the activities of the individual, their co-ordination and unification, as proceeding from the individual, point to a _substantial_ unity in the latter as their fundamental principle, a unity resulting from the _union of incomplete substances_.
This latter is undoubtedly the view of St. Thomas, of practically all the medieval scholastics, and of most scholastics in modern times. Nor do we see any sufficient reason for receding from it, or admitting the modern distinction between substance and nature.
And if it be objected that the view which admits the reality of incomplete substances and substantial change is as much a preconception as what we have called the atomic view of substance, our answer is, once more, that since we have no intellectual intuition into the real const.i.tution of the substances which const.i.tute the universe, since we can argue to this only by observing and reasoning from their activities on the principle _Operari requitur esse_, the evidence alone must decide which view of these substances is the correct one. Does the evidence afforded us by a scientific a.n.a.lysis of all the functions, inorganic, vegetative, sentient and rational, of an individual man, forbid us to conclude that he is one complete substance, resulting from the union of two incomplete substantial principles, a spiritual soul and a material principle? and at the same time compel us to infer that he is one complete nature resulting from the union of a plurality of principles supposed to be complete as substances and incomplete as natures? We believe that it does not; nor can we see that any really useful purpose is served by thus setting up a real distinction between substance and nature. From the evidence to hand it is neither more nor less difficult to infer unity of substance than unity of nature in the individual. The inference in question is an inference from facts in the phenomenal order, in the domain of the senses, to what must be actually there in the noumenal order, in the domain of nature or substance, a domain which cannot be reached by the senses but only by intellect. Nor will any imagination images which picture for us the physical fusion or coalescence of material things in the domain of the senses help us in the least to conceive in any positive way the mode in which incomplete natures or substances unite to form a complete nature or substance. For these latter facts belong to the domain which the senses cannot reach at all, and which intellect can reach only inferentially and not by direct insight.
Hence we consider the view which regards real unity of nature as compatible with real and actual plurality of complete substances in the individual, as improbable. At the same time we do not believe that this view is a necessary corollary from the real identification of essence with existence in created things. We have seen that even if accidents have their own existence in so far as they have their own essence-as they have if essence and existence be really identical-nevertheless the concrete substance as determined by its accidents can have a really unitary existence, _unum esse_ corresponding to and identical with its composite const.i.tution (67). Similarly, if the existence of each incomplete substance is identical with its incomplete essence, this is no obstacle to the complete substance-which results from the union of two such incomplete substantial principles-having one complete unitary existence identical with its composite essence.
Hence it is useless to argue against the view that a plurality of actually distinct and complete substances can unite to form a complete nature which will be really _one being_, on the ground that each complete substance has already its own existence and that things which have and preserve their own existence cannot form _one being_. Such an argument is inconclusive; for although _one being_ has of course only one existence, it has not been proved that this one existence cannot result from the union of many incomplete existences: especially if these existences be identical with the incomplete essences which are admittedly capable of uniting to form one complete essence.
It may, however, be reasonably urged against the opinion under criticism that, since the complete substances are supposed to remain complete and unchanged in their state of combination, it is difficult to see how this combination can be a real union and not merely an extrinsic juxtaposition,-one which remains in reality a merely accidental conjunction, even though we may dignify it with the t.i.tle of a "natural union".
And finally it may be pointed out that in this view the operations of the individual have not really _one ultimate_ intrinsic principle at all, since behind the supposed unity of nature there is a more fundamental plurality of actually distinct substances.
72. SUBSISTENCE AND PERSONALITY.-We have already examined the relation between the individual and the universal, between _first_ and _second_ substances, in connexion with the doctrine of Individuation (31-3). And we then saw that whatever it be that individuates the universal nature, it is at all events not to be regarded as anything extrinsic and superadded to this nature in the individual, as anything really distinct from this nature: that, for instance, what makes Plato"s human nature to be Plato"s is not anything really distinct from the human nature that is in Plato. We have now to fix our attention on the nature as individualized. We have to consider the complete individual nature or substance itself in actually existing individual "things" or "persons".
We must remember that scholastics are not agreed as to whether there is a real distinction or only a virtual distinction between the actual existence and the complete individual essence or substance or nature of created individual beings (21-4). Furthermore we have seen that philosophers who study the metaphysics of the inorganic world and of the lower forms of life are unable to say with certainty what is the individual in these domains: whether it is the chemical molecule or the chemical atom or the electron; whether it is the single living cell or the living ma.s.s consisting of a plurality of such cells (31). But we have also seen that as we ascend the scale of living things all difficulty in designating the genuine individual disappears: that a man, a horse, an oak tree, are undoubtedly individual beings.
Bearing these things in mind we have now to inquire into what has been called the _subsistence_ or _personality_ of the complete individual substance or nature: that perfection which enables us formally to designate the latter a "subsisting thing"(285) or a "person". By personality we mean the subsistence of a complete individual _rational_ nature. We shall therefore inquire into the meaning of the generic term _subsistentia_ (or _suppositalitas_), _subsistence_, in the abstract. But let us look at it first in the concrete.
A complete individual nature or substance, when it exists in the actual order, really distinct and separate in its own complete ent.i.ty from every other existing being, exercising its powers and discharging its functions of its own right and according to the laws of its own being, is said to _subsist_, or to have the perfection of _subsistence_. In this state it not only _exists in itself_ as every substance does; it is not only _incommunicable_ to any other being as every individual is, in contradistinction with _second_ or _universal_ substances which are, as such, indefinitely communicable to individuals; but it is also a complete whole, incommunicable _as a mere integral or essential part_ to some other whole, unlike the incomplete substantial const.i.tuents, or integral parts, members or organs of, say, an individual organic body; and finally it is incommunicable in the sense that it is not capable of being a.s.sumed into the subsisting unity of some other superior "suppositum" or "person". All those characteristics we find in the individual "subsisting thing" or "person". It "exists in itself" and is not communicable to another substance _as an accident_, because it is itself a substance. It is not communicable _to individuals as a universal_, because it is itself an individual. It is not communicable _as an integral or essential part to a whole_, because it is itself a complete substance and nature.(286) Finally it is not communicable to, and cannot be a.s.sumed into, the unity of a higher personality so as to subsist by virtue of the latter"s subsistence, because it has a perfection incompatible with such a.s.sumption, _viz._ its own proper subsistence, whereby it is already an actually subsisting thing or person in its own right, or _sui juris_, so to speak.
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 a.s.sumed 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 const.i.tutes 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 const.i.tute it a complete individual of the species to which it belongs, nevertheless if it is a.s.sumed 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 a.s.sumed. If an individual human nature be thus hypostatically or personally a.s.sumed 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 G.o.d-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 const.i.tutes 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 (?p?stas??, "_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 Boetius is cla.s.sic: "_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. p??s?p????, from p??s?p??, the face, countenance)-originally meaning a role 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 beings, who, as free agents, can more properly direct and control these actions.(291)
73. DISTINCTION BETWEEN THE INDIVIDUAL NATURE AND ITS SUBSISTENCE. WHAT CONSt.i.tUTES PERSONALITY?-Knowing now what we mean by the terms "subsistence," "suppositum," "person," and "personality," we have next to inquire in what precisely does subsistence consist. What is it that const.i.tutes a complete individual nature a "subsisting being," or if the nature be rational, a "person"? Subsistence connotes, over and above the mode of "existing in itself" which characterizes all substance, the notion that the substance or nature is individual, that it is complete, that it is in every way incommunicable, that it is _sui juris_ or autonomous in its existence and activities. These notions are all positive; they imply positive perfections: even incommunicability is really a positive perfection though the term is negative. But is any one of the positive perfections, thus contained in the notion of subsistence, a positive something _over and above_, and _really distinct from_, the perfection already implied in the concept of _a complete individual nature as such_?
Some of those philosophers who regard the distinction between essence and existence in creatures as a real distinction, identify the _subsistence_ of the complete individual nature with its _actual existence_, thus placing a real distinction between nature and subsistence or personality.(292) Apart from these, however, it is not likely that any philosophers, guided by the light of reason alone, would ever have held, or even suspected, that the subsistence of an actually existing individual nature is a positive perfection really distinct from, and superadded to, the latter. For we never, in our natural experience, encounter an existing individual substance, or nature, or agent, that is not distinct, autonomous, independent, _sui juris_, and incommunicable in its mode of being and acting.
Rigorously, however, this would only prove that subsistence is a perfection _naturally inseparable_ from the complete individual nature; _conceivably_ it _might_ still be _really_ distinct from the latter. But whether or not such real distinction could be suspected by the unaided light of reason working on natural experience, at all events what we know from Divine Revelation concerning the hypostatic union of the human nature of our Lord Jesus Christ with the Person of the Divine Word, enables us to realize that there _can_ be, in the actual order of things, a complete individual nature which is not a "subsisting being" or "person"; for the human nature of our Lord is _de facto_ such a nature,-and _ab actu ad posse valet consecutio_. This information, however, is not decisive in determining the character of the distinction between the individual substance or nature and its subsistence.
It may be that the complete individual nature is _eo ipso_ and identically a "subsisting being" or "person," that it is always independent, autonomous, _sui juris_, by the very fact that it is a complete individual nature, _unless it is_ DE FACTO _a.s.sumed into the personality of a higher nature_, so that in this intercommunication with the latter, in the unity of the latter"s personality, it is not independent, autonomous, _sui juris_, but dependent, subordinate, and _alterius juris_. In this condition, it loses nothing positive by the fact that it is not now a person and has not its own subsistence; nor does it gain any _natural_ perfection, for it was _ex hypothesi_ complete and perfect _as a nature_; but it gains something _supernatural_ inasmuch as it now subsists in a manner wholly undue to it.(293) According to this view, therefore, subsistence would not be a perfection really distinct from the complete individual nature; it would be a mentally distinct aspect of the latter, a positive aspect, however, consisting in this nature"s completeness, its self-sufficing, autonomous character, and consequent incommunicability.(294)
The princ.i.p.al difficulty against this view is a theological difficulty. As formulated by Urraburu,(295) it appears to involve an ambiguity in the expression "substantial union". It is briefly this: If the subsistence proper to a complete individual nature adds no positive perfection to the latter, so that the latter necessarily subsists and is a person unless it is actually a.s.sumed into a higher personality, and by the very fact that it is not actually so a.s.sumed, then the human nature of Christ "is as complete in every way and in every line of substantial perfection, by virtue of its own proper ent.i.ty, when actually united with the Divine Person, as it would be were it not so united, or as the person of Peter, or Paul, or any other human person is". But this implies that there are in Christ "two substances complete in every respect". Now between two such substances "there cannot be a substantial union," a union which would const.i.tute "one being,"
"unum per se ens". Hence the view in question would appear to be inadmissible.
But it is not proved that the union of "two substances complete in every respect" cannot result in the const.i.tution of a being that is really and genuinely one-"unum per se ens"-_in the case in which the union is a personal union_. The hypostatic union of the human nature of Christ with the Divine Person is primarily a _personal_ union whereby the former nature subsists by and in the Divine Personality. It has the effect of const.i.tuting the united terms "one subsisting being," and therefore has supereminently, if not formally, the effect of a "substantial union". Nay, it is a "substantial" union in the sense that it is a union of two substances, not of a substance and accidents; and also in the sense that it is not a mere accidental aggregation or artificial juxtaposition of substances, resulting merely in the const.i.tution of collective or artificial unity, a _unum per accidens_. But is it a "substantial" union in the sense that it is such a union of substances as results in one "nature"? Most certainly not; for this was the heresy of the Monophysites: that in Christ there is only one nature resulting from the union of the human nature with the Divine. If then, with Urraburu, we mean by "nature" simply "substance regarded as a principle of action" (71), and if, furthermore, the hypostatic union does not result in one "nature,"
neither does it result in one "substance," nor can it be a "substantial" or "natural" union in this sense.(296) He does not say, of course, that the hypostatic union is a "substantial union"
which results in "one nature," or even explicitly that it results in "one substance," but he says that the two substances are "substantially conjoined," "substantialiter conjunguntur"; and he continues, "a substantial union is such a conjunction of two substantial realities that there results from it one substantial something, which is truly and properly one"-"unio enim substantialis, est talis duarum rerum substantialium conjunctio, per quam resultat unum aliquid substantiale quod vere et proprie sit unum,"(297)-and he concludes that "there is something substantial wanting in the human nature of Christ, _viz._ personality, which, of course, is most abundantly supplied in the hypostatic union by the Divine Person"-"reliquum est, ut naturae humanae in Christo aliquid desit substantiale, nempe personalitas, quod per unionem hypostaticam c.u.mulatissime suppleatur a Verbo."(298) Now, this "aliquid substantiale" cannot be "aliquid naturale" in the sense that it is something _const.i.tutive_ of the human substance or nature; for the human substance or nature of Christ is certainly complete and perfect as a substance or nature.
It must be some complement or mode, that is naturally due to it, but supernaturally supplied by the Person of the Divine Word.(299) This brings us to the view that subsistence is a something positive, distinct in some real way, and not merely in our concepts, from the complete individual substance.
According to the more common view of catholic philosophers (and theologians) subsistence is some positive perfection really distinct from the complete individual nature. But the supporters of this general view explain it in different ways. We have already referred to the view of certain Thomists who, identifying _subsistence_ with the _actual existence_ of the complete substance or nature, place a real distinction between the existence and the substance or nature. Other Thomists, while defending the latter distinction, point out that actual existence confers no real perfection, but only actualizes the real; they hold, therefore, that subsistence is not existence, but is rather a perfection of the real, essential, or substantial order, as distinct from the existential order-a perfection presupposed by actual existence, and whose proper function is to _unify_ all the substantial const.i.tuents and accidental determinations of the individual substance or nature, thus making it a really unitary being-"unum ens per se"-proximately capable of being actualized by the simple existential act: which latter is the ultimate actuality of the real being: _esse est ultimus actus_.(300)
The concrete individual nature, containing as it does a plurality of really distinct principles, substantial and accidental, needs some unifying principle to make these one incommunicable reality, proximately capable of receiving a corresponding unitary existential act: without such a principle, they say, each of the substantial and accidental principles in the concrete individual nature would have its own existence: so that the result would be not _really_ one being, but a being really _manifold_ and only accidentally one-"unum per accidens". This principle is _subsistence_.
The human nature of our Divine Lord has not its own connatural subsistence; this is supplied by the subsistence of the Divine Person. Moreover, since the human nature in question has not its own subsistence, neither has it its own existence; existence is the actuality of the subsisting being; therefore there is in Christ but one existence, that of the Divine Person, whereby also the human nature of Christ exists.(301)
Of those who deny that the distinction between the existence and the essence of any created nature is a real distinction, some hold in the present matter the Scotist view that subsistence is not a positive perfection really distinct from the complete individual nature. Others, however, hold what we have ventured to regard as the more common view: that personality is something positive and really distinct from nature.
But they explain what they conceive subsistence to be without any reference to existence, and without distinguishing between the essential and the existential order of reality.
The most common explanation seems to be that subsistence is a unifying principle of the concrete individual nature, as stated above. Thus conceived, it is not an _absolute_ reality; nor is the distinction between it and the nature a _major_ real distinction. It is a _substantial mode_ (68), naturally superadded to the substance and modally distinct from the latter. It so completes and determines the substance or nature that the latter not only exists in itself but is also, by virtue of this mode, incommunicable in every way and _sui juris_.(302) It gives to the substance that ultimate determinateness which an accidental mode such as a definite shape or location gives to the accident of quant.i.ty.(303)
This mode is absent (supernaturally) from the human nature of our Divine Lord; this nature is therefore communicable; and the Personality of the Divine Word supernaturally supplies the function of this absent natural mode.
It must be confessed that it is not easy to understand how this or any other _substantial_ mode can be _really_ distinct from the substance it modifies. And in truth the distinction is not real in the full sense: it is not between _thing_ and _thing_, _inter rem et rem_. All that is claimed for it is that it is not merely mental; that it is not merely an _ens rationis_ which the mind projects into the reality; that it is a positive perfection of the nature or substance, a perfection which, though naturally inseparable from the latter, is not absolutely inseparable, and which, therefore, is _de facto_ supernaturally absent from the human nature and replaced by the Divine Personality in the case of the hypostatic union.