Actuality and Potentiality

Article 2. Actuality and Potentiality

a) Explanation of Terms　　b) Classification of Actuality and Potentiality　　c) Possibility　　d) Becoming or Change

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a) Explanation of Terms

A real being is, as we have seen, one that can exist independently of the created mind. Now, a real being that exists is actual; it has actuality; it is called ens in actu, that is, “a being in actuality.”

A real thing that can exist is, in so far, potential; it has potentiality; it is called ens in potentia, that is, “a being in potentiality.”

An existing being is actually what it is; potentially, however, it is what it may become. A baby is actually a baby; potentially, it is an adult. Cold water is actually cold; potentially, it is hot. A seed is actually a seed; potentially, it is a plant. Hydrogen and oxygen are actually hydrogen and oxygen; potentially they are water.

Therefore, an actual creature (i. e., an existing, finite, real being) is never pure actuality. It has within it an element of the potential. It is not merely that which is; it bears a real relation to that which has been, and involves the possibility or even the forecast of that which is to be and that which may be. For this reason, every actual creature is said to be compounded or composed of actuality and potentiality. It is what it is; and that is its actuality. It may become something other than it is, in accidental or in substance; and that is its potentiality.

b) Classification of Actuality and Potentiality

1. Actuality

(a) A creature, that is, a finite real being, is always composed of actuality and potentiality. It is therefore a mixed actuality. Now, a pure actuality, an actuality wholly unmixed with potentiality, must be an infinite being, possessing the fulness of all perfection in boundless degree, so that to lose anything or to gain anything, or to undergo any process of change, is entirely impossible. Pure actuality or actus purus is, therefore, the very definition of God.

(b) A first actuality, or actus primus, does not presuppose another actuality in the order to which itself belongs. A secondary actuality, or actus secundus, does presuppose such a prior actuality. Thus, actual activity,—such, for instance, as vital activity in a man,—is an actuality; but it is not a first actuality, for it presupposes the actually existing human essence equipped for such activity. The man is capable of vital action in the second place, after his essence has been constituted in the first place. Now, the human essence is formally constituted by the union of the actuating and active principle called the soul, with the organic body. Thus the human essence,—with its connatural activities,—is there in the second place after the soul has actuated the organism in the first place. The soul is the first actuality and the operating essence is the secondary actuality in this particular series of actualities. This fact, by the way, explains Aristotle’s definition of the soul as the “first act (or actuality) of the physical organic body.” We learn, in passing, that the terms first actuality and secondary actuality are not absolute, but relative; they are applied in certain series of actualities. Manifestly, if we were to speak absolutely, God is the first actuality, and the only one; for all other actualities presuppose the existence of the Infinite First Cause. But we have indicated this fact in our definition, for we said that a first actuality presupposes no other in the order to which it belongs itself. Philosophers use these terms first actuality and secondary actuality (or first act and second act) very frequently. We say, for example, that a baby is rational,—i. e., has understanding and free will,—in first act or in actu primo. After a few years, when the baby has acquired sufficient experience for the powers of understanding and will to be exercised consciously and reflexly, we say that it has come to the use of reason, and, in its actual operations of mind and will, it is now rational in second act or in actu secundo. The basic power of reasoning and willing,—though yet inoperative,—is rationality in first act; the actual exercise of this power is rationality in second act.

(c) We make a distinction between the actuality of essence (called actus essendi or actus essentiae) and the actuality of existence (called actus existendi or actus existentiae). The actuality of essence is that actuality by which a thing is constituted as a specific kind of thing. The actuality of existence is that actuality by which a definite essence is constituted as a thing which is here. Limiting our view to creatures, the act of existence,—or the actuality of existence,—is that actuality whereby an essence is not merely producible, but produced; not only causable, but caused; not only existible, but existent.

2. Potentiality

(a) Every existing or actual creature is subject to such agencies and forces as will make it different from what it now is. In other words, the potentiality or capability of becoming something else,—whether in essence or in non-essentials,—resides in it subjectively. This defines what we mean by subjective potentiality. That water, which is now actually cold, may become hot, is a potentiality resident in the water; it is subjective potentiality. That water may be presently changed substantially into hydrogen and oxygen is also a potentiality resident in the water as in its subject; more precisely, the potentiality in question resides in the prime matter which is the basic material constituent of water, which has here and now the substantial form of water, but which may undergo,—and hence is subject to,—the substantial change which will drive off the substantial form of water and, in the same instantaneous process, bring in the substantial forms of hydrogen and oxygen. The student will recall here a truth mentioned in many parts of philosophy, but which has its full explanation in Cosmology, namely, that the production of bodily substances (after their first creation) is always a process of substantial change, and that the gaining of a new substantial form is the losing of the old substantial form. This truth is expressed in the familiar axiom, generatio unius est corruptio alterius, “the generation (substantial production) of one bodily substance is the corruption (substantial reduction) of another.” The truth also holds conversely, corruptio unius est generatio alterius. We repeat, subjective potentiality is the capability or capacity resident in an existing creature (as in its subject) of becoming something other than it now is, whether in essence or in non-essentials.

Objective potentiality, on the other hand, is the possibility of a thing’s coming into existence. We may, somewhat illogically, define objective potentiality as the “capacity of a non-existent thing to receive existence.” Let us contrast the two types of potentiality discussed in this paragraph. The acorn is potentially an oak. This is subjective potentiality; it resides in the acorn as in a subject. But we may consider the oak itself (i. e., objectively) without reference to the acorn or any other thing, and view it merely as a reality which is not yet existent but which can be existent. In this view, the potentiality of the not-yet-existent oak is objective potentiality. The oak does not exist, but it can exist, and in this fact,—without considering the subject in which the capability of producing the oak is situate,—we discern its objective potentiality. In a word: subjective potentiality is a capacity in an existing thing; objective potentiality is the capacity for existence in a non-existent thing. Objective potentiality is neither more nor less than pure possibility (called also metaphysical, absolute, or objective possibility) of which we shall speak in another part of the present Article.

Subjective potentiality is more than pure possibility; it is, so to speak, the surety or promise of that which, in the natural course of events, is not merely capable of existing, but which is going to exist or may readily exist.

(b) Active potentiality is a form of subjective potentiality, and consists in the capacity or capability of an existing thing to act, to do something. Passive potentiality is a form of subjective potentiality, and consists in the capacity or capability of an existing thing to be acted upon, to receive something. The power to walk or to digest food is an active potentiality or active power. The power to be shaped into this figure or that (as in a lump of wax, for example) is a passive potentiality.

In its perfect form, active potentiality is not properly called potentiality at all. For in this form, the perfect form, it is identified with the perfect essence which is God, and God is actus purus, or pure actuality, having no slightest admixture of potentiality in His infinite being. God’s activity in creating, governing, concurring, and providing, by which His creatures have their being and their operations; His activity whereby the eternal processes of Generation and Procession take place within the Godhead, in no wise involves any change in God Himself. We rightly refer to God’s power to do all things as His omnipotence or His almightiness; we do not rightly refer to it as a potentiality. For this almighty power does not reside in God as in its subject; it is not, therefore, a subjective potentiality. This almighty power is one with God, identical with the divine essence itself; it is not something that God has; it is one with what God is; and God is Pure Actuality, excluding every slightest imperfection or potentiality. It will be understood, then, that when we speak of active potentiality and define it as the power to do something or to act, and ascribe this power to a being as the subject in which it resides, we are speaking of creatures only and of the capacities of creatures.

Active potentiality is usually understood by philosophers as a power or capability for taking hold of something and changing it. The digestive power of man, for example, lays hold of food and transforms it substantially into flesh and bone and tissue. The active powers which do not involve a change in the reality upon which they work, are usually called operative instead of active. Thus the power of reasoning, of thinking, or even of walking, is more properly called operative than active. It will be noticed in a moment that the term operative embraces not only active powers or potentialities, but certain passive potentialities as well.

Passive potentiality may be purely passive, as in the case of the block of marble which receives the form given it by the sculptor. Or passive potentiality may be receptive and re-active, as in the case of the sense of sight which receives the impression of a visible object and reacts to the stimulus of this impression and actively sees the object. This sort of passive potentiality is really passive, for the senses do receive their objects; they do not act upon them and change them as the digestive power acts upon and (substantially) changes food, or as the sculptor acts upon and (accidentally) changes the marble block. But this potentiality is not passive in a dead and inert manner; it is re-active. And we call it operative. Thus we find that the term operative potentiality or operative power includes those active powers which act upon their objects without changing them, and those passive potentialities which re-act to their objects and actively receive them.

(c) An active or a passive potentiality is called natural when it does not exceed the powers which belong to a reality when constituted in its own essential perfection. Thus the capacity for digesting food, walking, sensing, and growing larger, are natural potentialities in a young boy or girl. A potentiality (active or passive) is supernatural when it is a capacity bestowed, in excess of the requirements or capabilities of a created essence itself, by Almighty God. The term supernatural potentiality is usually restricted to the capacity of God’s rational creatures (men and angels) to receive,—under divine “enlargement” of their powers,—the gifts and graces whereby God is served, men’s hearts are won, or the Eternal Vision is enjoyed. Thus man’s capacity to receive grace is not from his own nature; his nature, as such, is incapable of receiving grace and has no essential claim to it; by God’s gift, by His “enlarging of nature,” man is capable of receiving the supernatural gift of grace. So, similarly, man is capable of receiving the gift of prophecy, or the gift of tongues, or the power to work miracles, or the Light of Glory for beholding God in heaven. In the case of bodily creatures less than men, the potentiality to re-act to God’s commands in a way that exceeds the normal capacities of their nature, is usually called obediential, to signify the fact that all creatures must obey their God, even in things that exceed their natural powers. Thus the potentiality of Aaron’s rod to become a living serpent when thrown before the throne of Pharao was obediential potentiality, as was the potentiality of the barren fig-tree to wither instantly at the word of Our Lord.

There are certain axioms which derive immediately from the ideas of actuality and potentiality. Of these we mention but a few that are more frequently quoted in philosophical treatises and discussions:

1. “Inasmuch as a thing is actual, it is perfect; inasmuch as it is constituted in potentiality it is imperfect.” Unumquodque secundum quod est actu est perfectum, secundum quod est in potentia est imperfectum. In other words, “actuality” and “potentiality” are synonyms respectively for “perfection” and “imperfection.” For the potentiality of a thing is a capacity unrealized, unactualized, and hence it involves a lack of perfection,—and the word perfection suggests a “thorough making” and a fulfillment,—which is given by actuality.

2. “Potentiality cannot actualize itself; it is actualized by something actual.” Potentia ut sic per se ad actum reduci nequit; reducitur ab alio principio in actu. That which is constituted in the state of potentiality, and is in so far imperfect, cannot give to itself what it does not possess, that is, actuality. Actuality must be conferred by a capable agency existing and functioning to actualize the potentiality in question.

3. “Absolutely speaking, actuality is prior to potentiality; but in a creature potentiality is prior to actuality.” Absolute prior est actus potentia; in ente autem mutabili prior est potentia actu. To illustrate: a cause must exist before it can produce its effect; it must be actual before it can actualize the objective potentiality of the effect. But no created cause exists which is not itself an effect, and hence, though now existing and actual, it came to actuality by the actualization of its own objective potentiality. Thus, the chain of creatures runs necessarily back to the absolute First Cause, the actus purus, and in this, absolutely speaking, we find the basic actuality, prior to all potentiality. But a creature must have potentiality before it can act or receive action, and here we find potentiality prior to actuality.

4. “Whatever is moved, is moved by something other than itself.” Quidquid movetur, ab alio movetur. Whatever is moved is, in so far, actualized; it is carried from a state of potentiality to actuality. And we have seen that potentiality cannot actualize itself. Movement does not mean local motion only; it means this, of course, but it means any transit from potentiality to actuality.

c) Possibility

Possibility is a word derived from the Latin possibilitas, which in turn is from the verb posse “to be able.” Possibility, therefore, by reason of its etymology, is that whereby a thing “is able” to exist. The clearest definition of possibility views the term negatively, and declares that possibility is the absence or non-existence of self-contradiction in the very concept or thought of a thing. If you analyze the concept or thought of a thing, and find that its elements are not in conflict,—if these elements do not contradict one another and refuse to be compounded,—then the thing is intrinsically possible. Thus the mountain of smooth glass which the hero in the fairy-tale had to climb in order to liberate the enchanted princess, is intrinsically possible. No such mountain exists on earth, and it is not likely that it ever will exist; but the point is that it could exist; there is no conflict or contradiction in the very thought of its existing. But “a square circle” is a conflict in itself; the elements of “square circle” are found to be contradictory, mutually cancelling each other, and hence the “square circle” cannot be thought of as an existing thing. Therefore, it is not intrinsically possible; on the contrary, it is intrinsically impossible. Intrinsic possibility and intrinsic impossibility are sometimes designated by the adjectives absolute, metaphysical, objective, as well as by the adjective intrinsic.

Anything intrinsically possible can, of course, be brought into existence by the boundless power of God. Things intrinsically impossible cannot be brought into existence at all. And this is not saying, as many thoughtless persons seem to think, that the infinite power of God is not really infinite after all, and that there are some things that God’s power cannot compass. For intrinsically impossible things are not true things or realities at all; they are logical beings or logical entities (entia logica or entia rationis). We call them “things” by a sort of extension or figure of speech, for we have no adequate simple term for them. An intrinsically impossible thing,—such, for instance, as “a square circle,“—inevitably cancels itself and turns to nothing when we try to conceive it in terms of reality. Thus, “a square circle” is neither more nor less than a circle which is not a circle. In other words it is nothing at all.

Anything, then, that is conceivable as a reality, anything that is thinkable as existing, whether as a fact it exists or not, is intrinsically possible; in other words, it has objective potentiality. Now, an intrinsically possible thing is said to be also extrinsically possible when there is a cause capable of conferring actual existence upon it. Therefore, every intrinsically possible thing is also extrinsically possible inasmuch as there exists an Almighty First Cause which can effect or produce it. But if we limit our view to the power of creatures,—to their active and operative potentialities,—we find that creatures (which are secondary causes) are not able to effect or produce every intrinsically possible thing. For many things which involve no self-contradiction are yet beyond the power of created causes (i. e., secondary causes) to produce. We say of such things that, while they are intrinsically possible, and also extrinsically possible to the primary cause (God), they are extrinsically impossible to the limited power of natural or secondary causes. Thus the glass mountain of the fairy-tale is a thinkable thing; it is intrinsically possible; it is also extrinsically possible to God; but it could not be produced by the natures or physes that we have available in this world, and so we say that it is physically impossible. To vary the language a bit, it is metaphysically possible (i. e., intrinsically), but physically impossible; it is absolutely possible, but relatively (i. e., in relation to the power of created natures) impossible; it is objectively possible (i. e., as an existible object or reality), but subjectively (i. e., with reference to the subjective potentiality of creatures) impossible.

Whatever is within the scope of natural powers (secondary causes) to effect is physically possible; whatever lies beyond this scope is physically impossible. It is physically possible for a man to master the works of St. Thomas Aquinas in many years; it is physically impossible for a man to master these works in a day. It is physically possible for a strong man to climb the Matterhorn; it is physically impossible for a baby to perform the same feat. It is physically possible for a sick man to show sudden and unexpected strength; it is physically impossible for a dead man to come back to earthly life. Whenever the power of God intervenes to produce an effect that is physically (but not metaphysically or intrinsically) impossible, we have a miracle. A miracle may be defined as a wondrous event, outside the ordinary course of nature, produced by Almighty God directly or through the instrumentality of creatures.

We have said that intrinsic possibility is absolute possibility. The term absolute is from the Latin absolutus which means “loosed from; freed from.” A thing absolutely possible is freed or loosed from any restricting considerations, such as “possible to unaided nature” or “possible in a certain way or under certain conditions.” Absolute or intrinsic possibility is the possibility of a thing considered in itself and not in special relations. Now, there is another view of possibility (extrinsic possibility, of course) which does see it in special relations, that is, in relation to the capacity of certain causes. This sort of possibility is not absolute, but relative. Physical possibility is one form of relative possibility; it is possibility in relation to, or relative to, the natures or physes of creatures. There is yet another form of relative possibility which views possibility in relation to, or relatively to, the effort or care which is expended in normal human conduct. This type of relative possibility is called moral possibility. The term moral does not suggest, in this present use, the issues of good and bad, right and wrong. The word is derived from the Latin mos (stem, mor-) which means characteristic human action or conduct. Thus the term moral here suggests merely what lies within the scope of normal human action. A thing is morally possible when,—being first intrinsically possible and also physically so,—it falls within the power of man when acting in a normal and characteristic way. Therefore, a thing which is physically possible is also morally so when a man can effect it without going beyond the normal human mode of action; in other words, a thing is morally possible when it can be effected by man without very great difficulty or the expenditure of very great exertion.

Thus it is physically possible for a man to walk three miles to Mass on Sunday, and also morally so. It is physically possible for a strong man to walk ten miles to Mass, but it is morally impossible. It is physically possible for an unskilled climber to scale a difficult mountain-peak, but it is morally impossible. It is physically possible for a speaker to enunciate every word of a lengthy oration with perfect intonation, stress, and correctness of emphasis, but it is morally impossible. It is physically possible for a motorist to observe every least traffic regulation for a full year together, but it is morally impossible. It is physically possible for a man to make a long and expensive journey for the purpose of gaining some unimportant bits of information, but it is morally impossible. In a word, that is morally impossible which is done with very great difficulty, or which involves outlay of effort or expense greater than ordinary human prudence would deem justified in the circumstances.

It is manifest that before a thing can be relatively possible, it must first be absolutely possible. Further, it is clear that before a thing can be morally possible, it must first be physically possible. Thus all possibility rests upon the ultimate basis of absolute or intrinsic possibility. We have now to inquire into the root-principle of intrinsic possibility itself.

All philosophers agree that intrinsic possibility means the absence of conflict or contradiction in the very concept or idea of a thing. But we have a question to answer which goes beyond this point of common agreement, and asks how it comes about that our ideas or concepts of intrinsically possible things are, as a fact, without conflict, while our ideas of intrinsically impossible things are self-contradictory. In other words, what, we ask, is the root-principle of intrinsic possibility?

1. Some theorists have held that the basic principle of intrinsic possibility is the actual existence of things. That things exist, they say, is proof positive that they can exist. Now, it is self-evidently true that actual existence is a proof of possible existence; the fact that a thing is is indubitable evidence that it can be. This is expressed in the ancient axiom, ab esse ad posse valet consecutio. But this truth does not constitute an answer to the question here proposed. We wish to know the ultimate principle of intrinsic possibility; we wish to know how it happens that intrinsically possible things are, as a fact, possible. We are not answered by the assertion that some possible things do exist and therefore can exist. The existence of a thing is proof of its possibility, but it is not an ultimate explanation of its possibility. We therefore reject the theory of actual existence as the root-principle of intrinsic possibility. We find that this theory misses the issue entirely; it does not explain what it purports to explain.

2. Other philosophers have taught that the ideas or concepts of things in the human mind constitute the ultimate principle of intrinsic possibility. The fact, they say, that we can think of a thing as existing is the principle of its existibility, that is, of its intrinsic possibility. But this theory would make the human mind the creator of its objects, which is not the case. Things in nature exist independently of the human mind; hence they have their existibility (or possibility) independently of that mind. We therefore reject the theory here proposed.

3. William of Ockham (1290–1347) declared that intrinsic possibility finds its ultimate principle or root in the power of God. But this doctrine would limit the divine and infinite power. Things intrinsically impossible would then be so only because God would lack power to effect them, which, as we have seen, cannot be the case. God’s power is indeed the ultimate principle of the extrinsic possibility of existible things, but not of their intrinsic possibility.

4. René Descartes (1596–1650) taught that intrinsic possibility depends ultimately upon God’s free will; things are possible because God chooses that they shall be so. But this doctrine would destroy the objective value of knowledge and render all human science impossible. For if it cannot be known that essences are constant, that they are necessarily and changelessly the same, our knowledge of essences (i. e., our ideas) must be transitory, unreliable, subject to change without notice. If, for example, the essence man or the essence circle (that is, the metaphysical essence, the things which these essences mean) could be changed by divine choice to an impossibility, our knowledge of what man means, or what circle means, would be no true knowledge at all. And, unless God in the supposed choice were to annihilate existing men, we should be faced with the absurdity of beholding utterly impossible human beings walking about; we should find the non-existible existing, and the impossible an actual fact. Were the free choice of the divine will to render actual essences impossible, we should find all our present knowledge of these things falsified, our sciences involving them futile and erroneous. Psychology, physiology, anatomy, hygiene, and all sciences which in any way touch the human essence would be rendered meaningless in the event that God should freely choose to make the essence man impossible. And should the divine choice make the essence circle impossible, geometry would go by the board. We are forced to reject the theory that the root-principle of intrinsic possibility is the free choice of God. God’s choice does determine which creatures shall exist, not which shall be possible.

5. To find the true principle of intrinsic possibility we must look to the divine mind, the divine intellect, the divine knowledge. We have learned that intrinsic possibility consists in the “thinkableness” of things. To borrow an analogy from secondary causes, we know that the architect must first think of the building in project; he must know it as existible; he must conceive it as a reality; else he cannot even begin to draw his plans. The sculptor must first know the image he is to produce, or he cannot even begin to produce it. The dressmaker must first know the garment she is about to make, or she cannot even begin to make it. In other words, before a thing is possible to one who can produce it, it must be thought of and known; it must exist in knowledge before it can exist in fact. Therefore, before anything is intrinsically possible, it must be known as existible in the mind of the First Infinite Cause. For this reason we say that the true principle of intrinsic possibility is the divine intellect. Now since God’s knowledge is one with His intellect, and His intellect is one with the divine essence itself, we say that the essence of God is the radical principle of intrinsic possibility, though the divine intellect is the formal principle of this possibility.

We must pause upon this doctrine for a brief space. God knows all things possible; He knows all things existible; He knows these things in His own divine essence, since His essence is one with His knowledge and His knowledge one with His essence. God knows all things possible and knows His power of choosing which of them He shall bring to actual existence. As the creating cause, the First Cause, God thus knows all things perfectly before they exist in fact, before any of them exist, before any scrap or shred of them or any “materials” for their making exist in fact. Now with creatures (secondary causes, since God is the sole primary cause or First Cause) the case is much different; indeed, the case is opposite. God, in His own essence, knows all possible things before any of them exist. Creatural causes, if they be rational (that is, if they be men or angels) must also know what is possible to their action before this exists; but creatures do not know what is possible to them in their own essence, nor eternally; creatures have learned what is producible from other things which actually exist. God does not learn; He knows perfectly, eternally, in His own essence. Rational creatures learn, they acquire knowledge, and it is always in the light of this acquired knowledge that they project future possibilities and plan things not yet existent. Hence, while the knowledge of a creature may reach forward into the realms of possibility, it also reaches backward and finds its support and foundation in the realm of things which actually exist. Even in projecting something new,—as the architect may envision new types of building, the sculptor new styles of artistic expression, the dressmaker new fashions,—the knowledge of a creature ever views the new in terms of the old; the new thing in project is a reshaping, recombining, rearranging of elements known from actual experience. Creatural activity can never bestow complete existence by a creative act, for creation is possible to God alone. Creatures can know things only from other things which exist; the elements which enter into the projected production must exist before they are known, for they must be learned. But with the First Cause all existibles, all things possible, must be perfectly known,—and not merely in their elements,—before they exist. Thus we see that all things possible depend essentially upon the divine intellect which perfectly knows them as possible, and fundamentally they depend upon the divine essence itself.

d) Becoming or Change

We have learned that a finite thing is what it is, and is in so far actual; but it came into being, and it involves the possibility of becoming something other than it is, in substance or in accidentals; indeed it is in constant process of becoming something else; and in so far it is potential. Thus the study of actuality and potentiality necessarily involves the topic of becoming or change.

A finite actuality is, as we have seen, never pure actuality; it is mixed with potentiality; it is a mixed actuality or actus mixtus, as philosophers say. Indeed, it is just to declare that it is composed of actuality and potentiality. Therefore, a finite actuality is not merely actual being; it is also actual and potential becoming.

So manifest is the fact of becoming or of change in the world about us, that certain philosophers, imitating the ancient Heraclitus and Protagoras (6 and 5 centuries b. c.), have declared that the very essence of things is change: “Nothing is, they say, all is becoming.” But this doctrine is not only destructive of objective truth; it is self-contradictory. If all consists in change, it is pertinent to ask what it is that continually changes. Baffled by this question, certain other philosophers veered completely about and denied the existence of becoming or change, saying that this is mere illusion: “All is,” they declare, “nothing becomes.” Such was the doctrine of Parmenides (6 century b. c.) and many a muddled philosopher followed him in teaching it. But the doctrine is wholly inadmissible. It makes nonsense of human knowledge, and it suggests that everything is part and parcel of Pure Actuality (that is, of God) and thus breeds pantheism, the most absurd of all false philosophies. The truth of course is that the world of finite actualities is also a world of potentialities; actual being exists and so does actual and potential becoming.

Now, becoming is a process of change. And change may be defined as a movement or transit from one state of being to another; it is a transition from potentiality to actuality. There are four types of change, three of which are accidental and one substantial. These types are: change of place or local change; change in amount or quantitative change; change in quality or qualitative change; change in substance or substantial change. The movement of a body from one place to another, or the movement of a part of a body with respect to other parts, is local change. The movement or transition of a body from smaller to larger, from larger to smaller, or the increasing or diminishing of the number or amount of elements or parts, is quantitative change. The change or movement from one quality to another, from hot to cold, from sweet to sour, from light-colored to dark-colored, from ignorance to knowledge, from virtue to vice, from joy to greater joy, is qualitative change. It will be noticed that qualitative change is not limited (as local change and quantitative change) to bodily things, but extends to the mental, the volitional, the spiritual. These three types of change are accidental since they affect a substance without affecting its nature or essence in a radical way; they modify, they qualify, they characterize a substance without transforming it into another substance. The fourth type of change is substantial change. It consists in the transition of a bodily thing (since spirits cannot be substantially changed) from one substantial state to another. The change of a living body to a dead body; the change of lifeless food into living blood and tissue and bone and sinew; the change of oxygen and hydrogen into water and of water into these two elements; the change of coal into ashes and smoke—all these are examples of substantial change.

Now, every change involves five things: (1) A thing to be changed whether substantially or accidentally. This is called the term from which (or the terminus a quo) the change moves or takes its beginning. (2) A thing resulting from the change, and this is the term to which (or the terminus ad quem) the change moves and in which it finds its completion or fulfillment. (3) An actual transition or movement (called the transitus) in which the change essentially or formally consists. (4) A substantial support for the change, and this remains unchanged in the process. (5) An agent or mover or motor-force which effects the transition.

The first three requirements of change are self-evidently necessary to it, and we need not pause to comment upon them. But a word must be said about the other two. We assert that every change requires a substantial support, a subject which remains itself unchanged. In accidental change, this support or subject is the substance affected by the change. When water is changed from cold to hot, the water itself is the subject and the support of the change-process. When a quart of water is increased to a gallon by the simple process of pouring more water into the container, the water itself is the subject which undergoes the change in quantity. When a soul is changed from the state of sin to the state of grace, the spiritual substance of the soul underlies the change. Notice that in all these changes, the substance which undergoes or underlies the change is itself unchanged. Water remains water while it passes from cold to hot, from a quart to a gallon; the soul remains the same soul, the same substance, while it passes from sin to grace.

There is no difficulty in understanding the necessity of a substantial support (itself unchanged) for accidental change. But we must notice the fact that there is an equal necessity for a substantial support (itself unchanged) for substantial change. If you change coal, for example, into ashes and smoke, you do not annihilate the coal and create the ashes and smoke. There is not, in this process of change, a complete breaking off of one actuality and a complete producing of other actualities. No, there must be something which underlies and supports the change, something which remains itself unchanged; and this something must be substantial, as is manifest from the nature of the case. We call this substantial something by the name prime matter or materia prima. Prime matter is the underlying substantial substrate of all bodies. It is not a definite kind of matter; it has no kinds of its own, no actuality of its own, no existence of its own or by itself; it is pure potentiality.

Every body is bodily, and its bodiliness is due to its prime matter. Every existing body is an actual body of a definite essential kind (lifeless, living, mineral, vegetal, animal, human), and all its actualness, and all its definiteness of specific kind, are due to the fact that prime matter is actualized in this essential and definite kind of being by another substantial reality called substantial form. Prime matter and substantial form are the ultimate substantial elements of any existing body. These are two substantial co-principles. Prime matter cannot exist by itself; and, unless it be spiritual (as in the case of the human soul, for example) substantial form cannot exist by itself. But the two come together to produce one complete and specific kind of actual bodily substance. Prime matter and substantial form are substantial; they are substances; but they are incomplete substances. They are complementary, one to the other, and from their union results, in each individual body, the actuality which we recognize as this existing, substantial bodily reality. Every existing body is, therefore, a compound of prime matter and substantial form. And when substantial change occurs,—as, for example, in the change from coal to ashes and smoke,—this is due to the fact that one substantial form gives way to another or to others, the prime matter remaining the same as the support or subject of the substantial change.

It is not within our present province to discuss the ultimate constitution of bodies; this study belongs to the department of philosophy known as Cosmology. But we must notice the fact that bodies are composed of prime matter and substantial form, in order to grasp the full meaning of substantial change. And out of this fact, which we have very briefly explained, emerge two inevitable conclusions, namely:

(1) The coming in of one substantial form is the driving out of another substantial form. There is no interval during which no substantial form holds prime matter in being; for prime matter is incapable of existence by itself. There is an ancient axiom which expresses this truth: generatio unius est corruptio alterius, “the generation (i. e., the substantial production) of one thing is the corruption (i. e., the substantial reduction or removal) of another.” The axiom holds also in the converse: corruptio unius est generatio alterius. The generation of water is the corruption of hydrogen and oxygen; the generation of hydrogen and oxygen is the corruption of water.

(2) Substantial change (i. e., generation and corruption) is instantaneous change; it is not progressive, successive, or gradual. When, for example, each tiny particle of coal is changed to ashes and smoke, a line is crossed, an immeasurable instant is passed, and the change has taken place. Up to that line, that instant, the substance was coal; beyond it, the substance is ashes and smoke. The instant itself is immeasurable. Similarly, in the substantial change called death, there is an immeasurable instant before which the living body is alive, after which it is dead, and the line itself is not to be reckoned in terms of duration; it is a measureless instant.

In passing, it is well to notice that creation is not substantial change, but complete and entire production. To create is to produce a thing in its entirety, there being no materials of any sort out of which the created thing is made. Therefore, the created object, the creature directly made by the creative act, is not changed from one substantial state to another. The “term from which” is lacking; there is no original substantial state from which the creature is drawn by the creative act. In like manner, annihilation is not a substantial change. Annihilation means the complete reduction of a reality to nothingness. Hence there is no substantial state to which change is made (i. e., no “term to which”), and the annihilated creature is not changed but totally destroyed. Creation is an operation requiring infinite power, and therefore is possible to God alone. Annihilation is the withdrawal of the creating and conserving power, and hence can be exercised only by the infinite being which has that power to withdraw. Creation accounts for the first production of bodily substances; thereafter, their origin is found in substantial change, i. e., in generation. Annihilation is within the absolute power of God, but does not occur, because it is not in harmony with the ordinated power of God, that is, with God’s power as seen in its infinite identity with His other perfections, such as His goodness, mercy, wisdom, justice.

We must now consider the final requirement of change, viz., the need of an agent, a motor-force, a mover, under the action of which the change is brought about. Change is movement, and nothing moves itself; a mover other than the thing moved is required. We have already seen the truth of this in our study of the principle Quidquid movetur ab alio movetur, “Whatever is moved is moved by something other than itself.” And in all activity of finite things, the verb to move is properly employed in the passive voice. We say, in casual speech, that an engine moves, or a stream moves, or a man moves, but, in each instance, the exact expression is “is moved” rather than “moves.” Self-movement, strictly understood, is a contradiction in terms and in thought. It involves the notion of a motionless thing giving itself motion, that is, giving to itself what it does not possess to give. Finite realities have activities, but these come from their capacities, and the capacities come in last analysis from the Creator. No creature moves itself from nothingness into existence. And, given existence, it operates by powers which belong to a nature which the creature did not give to itself, did not construct, and does not maintain in existence. A creature, that is, a limited agent or actor, is moved into existence, preserved in existence, dowered with powers for acting in a certain way; and all this happens by the action of existing causes (other than the creature affected by them), and ultimately by the infinite creator, the Actus Purus, the First Mover Himself Unmoved.

Summary of the Article

In this Article we have learned the meaning of actuality and potentiality, and have defined the varieties, pure actuality, mixed actuality; first actuality, secondary actuality; actuality of essence, actuality of existence; subjective potentiality, objective potentiality; active and passive potentiality; natural, supernatural, and obediential potentiality. We have set down certain axioms which derive immediately from the ideas of actuality and potentiality. We have studied the question of possibility, and have found that possibility is absolute and relative; and that relative possibility is either physical or moral. We have discussed various opinions about the root-principle of absolute or intrinsic possibility, and have concluded that this principle is, formally, the divine intellect, and, fundamentally, the divine essence. We have investigated the topic of becoming or change, defining it, indicating its types, and explaining its requirements.