9. (c) Actuality: Its Relation to Potentiality.—It is from our experience of change in the world that we derive our notions of the potential and the actual, of active power and passive potentiality. The term “act” has primarily the same meaning as “action,” “operation,” that process by which a change is wrought. But the Latin word actus (Gr. ἐνέργεια, ἐντελέχεια) means rather that which is achieved by the actio, that which is the correlative and complement of the passive potentiality, the actuality of this latter: that by which potential being is rendered formally actual, and, by way of consequence, this actual being itself. “Potentia activa” and its correlative “actus” might, perhaps, be appropriately rendered by “power” (potestas agendi) and “action” or “operation”; “potentia passiva” and its correlative “actus,” by “potentiality” and “actuality” respectively.
In these correlatives, the notion underlying the term “actual” is manifestly the notion of something completed, achieved, perfected—as compared with that of something incomplete, imperfect, determinable, which is the notion of the potential. Hence the notions of potentia and actus have been extended widely beyond their primary signification of power to act and the exercise of this power. Such pairs of correlatives as the determinable and the determined, the perfectible and the perfected, the undeveloped or less developed and the more developed, the generic and the specific, are all conceived under the aspect of this widest relation of the potential to the actual. And since we can distinguish successive stages in any process of development, or an order of logical sequence among the contents of our concept of any concrete reality, it follows that what will be conceived as an actus in one relation will be conceived as a potentia in another. Thus, the disposition of any faculty—as, for example, the scientific habit in the intellect—is an actus or perfection of the faculty regarded as a potentia; but it is itself a potentia which is actualized in the operation of actually studying. This illustrates the distinction commonly drawn between an “actus primus” and an “actus secundus” in any particular order or line of reality: the actus primus is that which presupposes no prior [pg 057] actuality in the same order; the actus secundus is that which does presuppose another. The act of knowing is an actus secundus which presupposes the cognitive faculty as an actus primus: the faculty being the first or fundamental equipment of the soul in relation to knowledge. Hence the child is said to have knowledge “in actu primo” as having the faculty of reason; and the student to have knowledge “in actu secundo” as exercising this faculty.
The actus or perfecting principles of which we have spoken so far are all conceived as presupposing an existing subject on which they supervene. They are therefore accidents as distinct from substantial constitutive principles of this subject; and they are therefore called accidental actualities, actus “accidentales”. But the actual existence of a being is also conceived as the complement and correlative of its essence: as that which makes the latter actual, thus transferring it from the state of mere possibility. Hence existence also is called an actus or actuality: the actus “existentialis,” to distinguish it from the existing thing's activities and other subsequently acquired characters. In reference to these existence is a “first actuality”—“Esse est actus primus”; “Prius est esse quam agere”: “Existence is the first actuality”; “Action presupposes existence”—while each of these in reference to existence, is a “second actuality,” an actus secundus.
When, furthermore, we proceed to examine the constitutive principles essential to any being in the concrete, we may be able to distinguish between principles which are determinable, passive and persistent throughout all essential change of that being, and others which are determining, specifying, differentiating principles. In water, for example, we may distinguish the passive underlying principle which persists throughout the decomposition of water into oxygen and hydrogen, from the active specifying principle which gives that substratum its specific nature as water. The former or material principle (ὕλη, materia) is potential, compared with the latter or formal principle (μορφή, εἶδος, ἐντελέχεια, forma, species, actus) as actual. The concept of actus is thus applied to the essence itself: the actus “essentialis” or “formalis” of a thing is that which we conceive to be the ultimate, completing and determining principle of the essence or nature of that thing. In reference to this as well as the other constitutive principles of the thing, the actual existence of the thing is a “second actuality,” an actus secundus.
In fact all the constitutive principles of the essence of any existing thing, and all the properties and attributes involved in the essence or necessarily connected with the essence, must all alike be conceived as logically antecedent to the existential actus whereby they are constituted something in the actual order, and not mere possible objects of our thought. And from this point of view the existence of a thing is called the ultimate actualization of its essence. Hence the scholastic aphorism: “Esse est ultimus actus rei”.
The term actus may designate that complement of reality by which potential being is made actual (actus “actuans”), or this actual being itself (actus “simpliciter dictus”). In the latter sense we have already distinguished the Being that is immutable, the Being of God, as the Actus Purus, from the being of all mutable things, which latter being is necessarily a mixture of potential and actual, an actus mixtus.
Now if the essences of corporeal things are composite, if they are constituted by the union of some determining, formative principle with a determinable, passive principle—of “form” with “matter,” in scholastic terminology—we may call these formative principles actus “informantes”; and if these cannot actually exist except in union with a material principle they may be called actus “non-subsistentes”: e.g., the formative principle or “forma substantialis” of water, or the vital principle of a plant. If, on the other hand, there exist essences which, being simple, do not actualize any material, determinable principle, but subsist independently of any such, they are called actus “non-informantes,” or actus “subsistentes”. Such, for example, are God, and pure spirits whose existence is known from revelation. Finally, there may be a kind of actual essence which, though it naturally actualizes a material principle de facto, can nevertheless continue to subsist without this latter: such an actual being would be at once an actus informans and an actus subsistens; and such, in fact, is the human soul.
Throughout all distinctions between the potential and the actual there runs the conception of the actual as something more perfect than the potential. There is in the actual something positive and real over and above what is in the potential. This is an ultimate fact in our analysis; and its importance will be realized when we come to apply the notions we have been explaining to the study of change.
The notion of grades of perfection in things is one with which everyone is familiar. We naturally conceive some beings as higher upon the scale of reality than others; as having “more” reality, so to speak—not necessarily, of course, in the literal sense of size or quantity—than others; as being more perfect, nobler, of greater worth, value, dignity, excellence, than others. Thus we regard the infinite as more perfect than the finite, spiritual beings as nobler than material beings, man as a higher order of being than the brute beast, this again as surpassing the whole vegetable kingdom, the lowest form of life as higher on the scale of being than inorganic matter, the substance-mode of being as superior to all accident-modes, the actualized state of a being as more perfect than its potential state, i.e. as existing in its material, efficient and ideal or exemplar causes. The grounds and significance of this mental appreciation of relative values in things must be discussed elsewhere. We refer to it here in order to point out another scholastic aphorism, according to which the higher a thing is in the scale of actual being, and the more perfect it is accordingly, the more efficient it will also be as a principle of action, the more powerful as a cause in the production of changes in other things, the more operative in actualizing their passive potentialities; and conversely, the less actual a thing is, and therefore the more imperfect, the greater its passive capacity will be to undergo the influence of agencies that are actual and operative around it. “As passive potentiality,” says St. Thomas,[74] “is the mark of potential being, so active power is the mark of actual being. For a thing acts, in so far as it is actual; but is acted on, so far as it is potential.” Our knowledge of the nature of things is in fact exclusively based on our knowledge of their activities: we have no other key to the knowledge of what a thing is than our knowledge of what it does: “Operari sequitur esse”: “Qualis est operatio talis est natura”—“Acting follows being”: “Conduct is the key to nature”.
A being that is active or operative in the production of a change is said to be the efficient cause of the change, the latter being termed the effect. Now the greater the change, i.e. the higher and more perfect be the grade of reality that is actualized in the change, the higher too in the scale of being must be the efficient cause of that change. There must be a proportion in degree of perfection or reality between effect and cause. The [pg 060] former cannot exceed in actual perfection the active power, and therefore the actual being, of the latter. This is so because we conceive the effect as being produced or actualized through the operative influence of the cause, and with real dependence on this latter; and it is inconceivable that a cause should have power to actualize other being, distinct from itself, which would be of a higher grade of excellence than itself. The nature of efficient causality, of the influence by which the cause is related to its effect, is not easy to determine; it will be discussed at a subsequent stage of our investigations (ch. [xi.]); but whatever it be, a little reflection should convince us of the truth of the principle just stated: that an effect cannot be more perfect than its cause. The mediæval scholastics embodied this truth in the formula: Nemo dat quod non habet—a formula which we must not interpret in the more restricted and literal sense of the words giving and having, lest we be met with the obvious objection that it is by no means necessary for a boy to have a black eye himself in order to give one to his neighbour! What the formula means is that an agent cannot give to, or produce in, any potential subject, receptive of its causal influence, an actuality which it does not itself possess virtually, or in its active power: that no actuality surpassing in excellence the actual perfection of the cause itself can be found thus virtually in the active power of the latter. There is no question of the cause or agent transferring bodily as it were a part of its own actuality to the subject which is undergoing change[75]; nor will such crude imagination images help us to understand what real change, under the influence of efficient causality, involves.[76] An analysis of change will enable us to appreciate more fully the real difficulty of explaining it, and the futility of any attempt to account for it without admitting the real, objective validity of the notions of actual and potential being, of active powers or forces and passive potentialities in the things that are subject to change.