In this solution of the question it is not easy to see how the material principle, which, by its alliance with quantity, individuates the form, is itself individuated so as to be the source and principle of a multiplicity of numerically distinct and incommunicable realizations of this form. Perhaps the most that can be said on this point is that we must conceive quantity, which is the fundamental property of corporeal reality, as being itself essentially divisible, and the material principle as deriving from its essential relation to quantity its function of multiplying the same specific nature numerically.

Of those who reject the Thomistic doctrine some few contend that it is the actual existence of any specific nature that should be conceived as individuating the latter. No doubt the universal as such cannot exist; reality in order to exist actually must be individual. Yet it cannot be actual existence that individuates it. We must conceive it as individual before conceiving it as actually existent; and we can conceive it as individual while abstracting from its existence. We can think, for instance, of purely possible individual men, or angels, as numerically or individually distinct from one another. Moreover, what individuates the nature must be essential to the latter, but actual existence is not essential to any finite nature. Hence actual existence cannot be the principle of individuation.[149] Can it be contended that possible existence is what individuates reality? No; for possible existence is nothing more than intrinsic capacity to exist actually, and this is essential to all reality: it is the criterion whereby we distinguish real being [pg 132] from logical being; but real being, as such, is indifferent to universality or individuality; as far as the simple concept of real being is concerned the latter may be either universal or individual; the concept abstracts equally from either condition of being.

The vast majority, therefore, of those who reject the Thomistic doctrine on individuation, support the view that what individuates any nature or substance is simply the whole reality, the total entity, of the individual. This total entity of the individual, though really identical with the specific nature, must be conceived as something positive, superadded to the latter, for it involves a something which is logically or mentally distinct from the latter. This something is what we conceive as a differentia individua, after the analogy of the differentia specifica which contracts the concept of the genus to that of the species; and by Scotists it has been termed “haecceitas” or “thisness”. Without using the Scotist terminology, most of those scholastics who reject the Thomist doctrine on this point advocate the present view. The individuality or “thisness” of the individual substance is regarded as having no special principle in the individual, other than the whole substantial entity of the latter. If the nature is simple it is of itself individual; if composite, the intrinsic principles from which it results—i.e. matter and form essentially united—suffice to individuate it.

In this view, therefore, the material principle of any individual man, for example, is numerically and individually distinct from that of any other individual, of itself and independently of its relation either to the formative principle or to quantity. The formative principle, too, is individuated of itself, and not by the material principle which is really distinct from it, or by its relation to this material principle. Likewise the union of both principles, which is a substantial mode of the composite substance, is individuated and rendered numerically distinct from all other unions of these two individual principles, not by either or both these, but by itself. And finally, the individual composite substance has its individuation from these two intrinsic principles thus individually united.

It may be doubted, perhaps, whether this attempt at explaining the real, individual “manifoldness” of what is “one” for intellect, i.e. the universal, throws any real light upon the problem. No doubt, every element or factor which is grasped by intellect in its analysis of reality—matter, form, substance, [pg 133] accident, quantity, nay, even “individuality” itself—is apprehended as abstract and universal; and if we hold the doctrine of Moderate Realism, that the intellect in apprehending the universal attains to reality, and not merely to a logical figment of its own creation, the problem of relating intelligibly the reality which is “one” for intellect with the same reality as manifestly “manifold” in its concrete realizations for sense, is a genuine philosophical problem. To say that what individuates any real essence or nature, what deprives it of the “oneness” and “universality” which it has for intellect, what makes it “this,” “that,” or “the other” incommunicable individual, must be conceived to be simply the whole essential reality of that nature itself—leaves us still in ignorance as to why such a nature, which is really “one” for intellect, can be really “manifold” in its actualizations for sense experience. The reason why the nature which is one and universal for abstract thought, and which is undoubtedly not a logical entity but a reality capable of actual existence, can be actualized as a manifold of distinct individuals, must be sought, we are inclined to think, in the relation of this nature to a material principle in alliance with quantity which is the source of all purely numerical, “space and time” distinctions.

33. Individuation of Accidents.—The rôle of quantity in the Thomistic theory of individuation suggests the question: How are accidents themselves individuated? We have referred already ([29], n.) to the view that they are individuated by the individual subjects or substances in which they inhere. If we distinguish again between what reveals individuality and what constitutes it, there can be no doubt that when accidents of the same kind are found in individually distinct subjects what reveals the numerical distinction between the former is the fact that they are found inhering in the latter. So, also, distinction of individual substances is the extrinsic, genetic, or causal principle of the numerical distinction between similar accidents arising in these substances. But when the same kind of accident recurs successively in the same individual substance—as, for example, when a man performs repeated acts of the same kind—what reveals the numerical or individual distinction between these latter cannot be the individual substance, for it is one and the same, but rather the time distinction between the accidents themselves.

The intrinsic constitutive principle which formally individuates the accidents of individually distinct substances is, according to Thomists generally, their essential relation to the individual substances in which they appear. It is not clear how this theory can be applied to the fundamental accident of corporeal substances. If the function of formally individuating the corporeal substance itself is to be ascribed in any measure to quantity, it would seem [pg 134] to follow that this latter must be regarded as individuated by itself, by its own total entity or reality. And this is the view held by most other scholastics in regard to the individuation of accidents generally: that these, like substances, are individuated by their own total positive reality.

When there is question of the same kind of accident recurring in the same individual subject, the “time” distinction between such successive individual accidents of the same kind would appear not merely to reveal their individuality but also to indicate a different relation of each to its subject as existing at that particular point of space and time: so that the relation of the accident to its individual subject, as here and now existing in the concrete, would be the individuating principle of the accident.

Whether a number of accidents of the same species infima, and distinct merely numerically, could exist simultaneously in the same individual subject, is a question on which scholastic philosophers are not agreed: the negative opinion, which has the authority of St. Thomas, being the more probable. Those various questions on the individuation of accidents will be better understood from a subsequent exposition of the scholastic doctrine on accidents (Ch. [viii.]).

It may be well to remark that in inquiring about the individuation of substances and accidents we have been considering reality from a static standpoint, seeking how we are to conceive and interpret intellectually, or for abstract thought, the relation of the universal to the individual. If, however, we ascribe to “time” distinctions any function in individuating accidents of the same kind in the same individual substance, we are introducing into our analysis the kinetic aspect of reality, or its subjection to processes of change.