CHAPTER II. BECOMING AND ITS IMPLICATIONS.

6. THE STATIC AND THE CHANGING.—The things we see around us, the things which make up the immediate data of our experience, not only _are_ or _exist_; they also _become_, or _come_ into actual existence; they _change_; they pass out of actual existence. The abstract notion of being represents its object to the mind in a static, permanent, changeless, self-identical condition; but if this condition were an adequate representation of reality change would be unreal, would be only an illusion. This is what the Eleatic philosophers of ancient Greece believed, distinguishing merely between being and nothingness. But they were mistaken; for change in things is too obviously real to be eliminated by calling it an illusion: even if it were an illusion, this illusion at least would have to be accounted for. In order, therefore, to understand reality we must employ not merely the notion of being (something _static_), but also the notion of becoming, change, process, appearing and disappearing (something _kinetic_, and something _dynamic_). In doing so, however, we must not fall into the error of the opposite extreme from the Eleatics—by regarding change as the adequate representation of reality. This is what Heraclitus and the later Ionians did: holding that nothing _is_, that all _becomes_ (πάντα ρέι), that change is all reality, that the stable, the permanent, is non-existent, unreal, an illusion. This too is false; for change would be unintelligible without at least an abiding _law_ of change, a permanent _principle_ of some sort; which, in turn, involves the reality of some sort of abiding, stable, permanent being.

We must then—with Aristotle, as against both of those one-sided conceptions—hold to the reality both of being and of becoming; and proceed to see how the stable and the changing can both be real.

To convince ourselves that they are both real, very little reflection is needed. We have actual experience of both those elements of reality in our consciousness and memory of our own selves. Every human individual in the enjoyment of his mental faculties knows himself as an abiding, self-identical being, yet as constantly undergoing real changes; so that throughout his life he is really the same being, though just as certainly he really changes. In external nature, too, we observe on the one hand innumerable processes of growth and decay, of motion and interaction; and on the other hand a similarly all-pervading element of sameness or identity amid all this never-ending change.

7. THE POTENTIAL AND THE ACTUAL. (_a_) POSSIBILITY, ABSOLUTE, RELATIVE, AND ADEQUATE.—It is from our experience of actuality and change that we derive not only our notion of temporal duration, but also our notion of _potential being_ or _possibility_, as distinct from that of _actual being_ or _actuality_. It is from our experience of what actually exists that we are able to determine what can, and what cannot exist. We know from experience what gold is, and what a tower is; and that it is intrinsically possible for a golden tower to exist, that such an object of thought involves no contradiction, that therefore its existence is not impossible, even though it may never actually exist as a fact. Similarly, we know from experience what a square is, and what a circle is; and that it is intrinsically impossible for a square circle to exist, that such an object of thought involves a contradiction, that therefore not only is such an object never actually existent in fact, but that it is in no sense real, in no way possible.

Thus, _intrinsic_ (or _objective_, _absolute_, _logical_, _metaphysical_) possibility is the mere non-repugnance of an object of thought to actual existence. Any being or object of thought that is conceivable in this way, that can be conceived as capable of actually existing, is called intrinsically (or objectively, absolutely, logically, metaphysically) possible being. The absence of such intrinsic capability of actual existence gives us the notion of the intrinsically (objectively, absolutely, logically, metaphysically) impossible. We shall return to these notions again. They are necessary here for the understanding of real change in the actual universe.

Fixing our attention now upon the real changes which characterize the data of our experience, let us inquire what conditions are necessary in order that an intrinsically possible object of thought become here and now an actual being. It matters not whether we select an example from the domain of organic nature, of inorganic nature, or of art—whether it be an oak, or an iceberg, or a statue. In order that there be here and now an actual oak-tree, it is necessary not only (1) that such an object be intrinsically possible, but (2) that there have been planted here an actual acorn, _i.e._ an actual being having in it subjectively and really the passive potentiality of developing into an actual oak-tree, and (3) that there be in the actual things around the acorn active powers or forces capable of so influencing the latent, passive potentiality of the acorn as gradually to evolve the oak-tree therefrom. So, too, for the (1) intrinsically possible iceberg, there are needed (2) water capable of becoming ice, and (3) natural powers or forces capable of forming it into ice and setting this adrift in the ocean. And for the (1) intrinsically possible statue there are needed (2) the block of marble or other material capable of becoming a statue, and (3) the sculptor having the power to mould this material into an actual statue.

In order, therefore, that a thing which is not now actual, but only intrinsically or absolutely possible, become actual, there must actually exist some being or beings endowed with the _active power or potency_ of making this possible thing actual. The latter is then said to be _relatively, extrinsically_ possible—in relation to such being or beings. And obviously a thing may be possible relatively to the power of one being, and not possible relatively to lesser power of another being: the statue that is intrinsically possible in the block of marble, may be extrinsically possible relatively to the skilled sculptor, but not relatively to the unskilled person who is not a sculptor.

Furthermore, relatively to the same agent or agents, the production of a given effect, the doing of a given thing, is said to be _physically_ possible if it can be brought about by such agents acting according to the ordinary course of nature; if, in other words they have the physical power to do it. Otherwise it is said to be physically impossible, even though metaphysically or intrinsically possible, _e.g._ it is physically impossible for a dead person to come to life again. A thing is said to be _morally_ possible, in reference to free and responsible agents, if they can do it without unreasonable inconvenience; otherwise it is considered as morally impossible, even though it be both physically and metaphysically possible: as often happens in regard to the fulfilment of one’s obligations.

That which is _both intrinsically and extrinsically possible_ is said to be _adequately possible_. Whatever is intrinsically possible is also extrinsically possible in relation to God, who is _Almighty_, _Omnipotent_.

8. (_b_) SUBJECTIVE “POTENTIA,” ACTIVE AND PASSIVE.—Furthermore, we conceive the Infinite Being, Almighty God, as capable of _creating_, or producing actual being _from nothingness_, _i.e._ without any actually pre-existing material out of whose passive potentiality the actual being would be developed. Creative power or activity does not need any pre-existing subject on which to exercise its influence, any subject in whose _passive potentiality_ the thing to be created is antecedently implicit.

But all other power, all activity of created causes, does require some such actually existing subject. If we examine the activities of the agencies that fall within our direct experience, whether in external nature or in our own selves, we shall find that in no case does their operative influence or causality extend beyond the production of changes in existing being, or attain to the production of new actual being out of nothingness. The forces of nature cannot produce an oak without an acorn, or an iceberg without water; nor can the sculptor produce a statue except from some pre-existing material.

The _natural_ passive potentiality of things is, moreover, limited in reference to the active powers of the created universe. These, for example, can educe life from the passive potentiality of inorganic matter, but only by assimilating this matter into a living organism: they cannot restore life to a human corpse; yet the latter has in it the capacity to be restored to life by the direct influence of the Author of Nature. This special and supernatural potentiality in created things, under the influence of Omnipotence, is known as _potentia obedientalis_.(72)

This consideration will help us to realize that all reality which is produced by change, and subject to change, is essentially a mixture of _becoming_ and _being_, of _potential_ and _actual_. The reality of such being is not _tota simul_. Only immutable being, whose duration is _eternal_, has its reality _tota simul_: it alone is _purely actual_, the “_Actus Purus_”; and its duration is one eternal “_now_,” without beginning, end, or succession. But mutable being, whose duration in actual existence is measured by _time_, is actualized only successively: its actuality at any particular instant does not embody the whole of its reality: this latter includes also a “_was_” and “_will be_”; the thing was _potentially_ what it now is _actually_, and it will become actually something which it now is only potentially; nor shall we have understood even moderately the nature or essence of any mutable being—an oak-tree, for example—until we have grasped the fact that the whole reality of its nature embraces more than what we find of it actually existing at any given instant of its existence. In other words, we have to bear in mind that the reality of such a being is not pure actuality but a mixture of potential and actual: that it is an _actus non-purus_, or an _actus mixtus_.

We have to note well that the _potential being_ of a thing is something _real_—that it is not merely a _modus loquendi_, or a _modus intelligendi_. The oak is in the acorn in some true and real sense: the potentiality of the oak is something real in the acorn: if it were not so, if it were nothing real in the acorn, we could say with equal truth that a man or a horse or a house is potentially in the acorn; or, again with equal truth, that the oak is potentially in a mustard-seed, or a grain of corn, or a pebble, or a drop of water. Therefore the oak is _really_ in the acorn—not actually but potentially, _potentia passiva_.

The oak-tree is also really in those _active_ forces of nature whose influence on the acorn develop the latter into an actual oak-tree: it is in those causes not actually, of course, but _virtually_, for they possess in themselves the _operative power_—_potentia activa sive operativa_—to educe the oak-tree out of the acorn. These two potential conditions of a being—in the active causes which produce it, and in the pre-existing actual thing or things from which it is produced—are called each a real or subjective potency, _potentia realis_, or _potentia subjectiva_, in distinction from the mere logical or objective possibility of such a being.

And just as the passive potentiality of the statue is something real in the block of marble, though distinct from the actuality of the statue and from the process by which this is actualized, so is the active power of making the statue something real in the sculptor, though distinct from the operation by which he makes the statue. If an agent’s _power_ to act, to produce change, were not a reality in the agent, a reality distinct from the _action_ of the latter; or if a being’s capacity to undergo change, and thereby to become something other, were not a reality distinct from the process of change, and from the actual result of this process—it would follow not only that the actual alone is real, and the merely possible or potential unreal, but also that no change can be real, that nothing can really become, and nothing really disappear.(73)

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 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 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.

10. ANALYSIS OF CHANGE.—_Change_ (_Mutatio_, _Motus_, μεταβολή, κίνησις) is one of those simplest concepts which cannot be defined. We may describe it, however, as _the transition of a being from one state to another_. If one thing entirely disappeared and another were substituted for it, we should not regard the former as having been changed into the latter. When one thing is put in the place of another, each, no doubt, undergoes a change of place, but neither is changed into the other. So, also, if we were to conceive a thing as absolutely ceasing to exist, as lapsing into nothingness at a given instant, and another as coming into existence out of nothingness at the same instant (and in the same place), we should not consider this double event as constituting a real change of the former thing into the latter. And although our _senses_ cannot testify to anything beyond _sequence_ in sense phenomena, our _reason_ detects in real change something other than a total substitution of things for one another, or continuous total cessations and inceptions of existence in things. No doubt, if we conceive the whole phenomenal or perceptible universe and all the beings which constitute this universe as essentially contingent, and therefore dependent for their reality and their actual existence on a Supreme, Necessary Being who created and conserves them, who at any time may cease to conserve any of them, and produce other and new beings _out of nothingness_, then such absolute cessations and inceptions of existence in the world would not be impossible. God might _annihilate_, _i.e._ cease to conserve in existence, this or that contingent being at any instant, and at any instant _create_ a new contingent being, _i.e._ produce it in its totality from no pre-existing material. But there is no reason to suppose that this is what is constantly taking place in Nature: that all change is simply a series of annihilations and creations. On the contrary, the modes of being which appear and disappear in real change, in the transition of anything from one state to a really different state of being, do not appear _de novo_, _ex nihilo_, as absolute beginnings out of nothingness; or disappear _totaliter_, _in nihilum_, as absolute endings or lapses of reality into nothingness. The real changes which take place in Nature are due to the operation of natural causes. These causes, being finite in their operative powers, cannot create, _i.e._ produce new being from nothingness. They can, however, with the concurrence of the Omnipotent Being, modify existing modes of being, _i.e._ make actual what was only potential in these latter. The notion of change is not verified in the conception of successive annihilations and creations; for there is involved in the former concept not merely the notion of a real difference between the two _actual_ states, that before and that after the change, but also the notion of some _potential_ reality persisting throughout the change, something capable of being actually so and so before the change and actually otherwise after the change. For real change, therefore, we require (1) two positive and really different states of the same being, a “_terminus a quo_” and a “_terminus ad quem_”; and (2) a real process of transition whereby something potential becomes actual. In creation there is no real and positive _terminus a quo_; in annihilation there is no real and positive _terminus ad quem_; these therefore are not changes in the proper sense of the term. Sometimes, too, change is affirmed, by purely extrinsic denomination, of a thing in which there is no real change, but only a relation to some other really changing thing. In this sense when an object unknown or unthought of becomes the actual object of somebody’s thought or cognition, it is said to “change,” though the transition from “unknown” to “known” involves no real change of state in the object, but only in the knowing subject. If thought were in any true sense “constitutive” of reality, as many modern philosophers contend, the change in the object would of course be real.

Since, therefore, change consists in this, that a thing which is actually in a given state ceases to be actually such and begins to be actually in another state, it is obvious that there persists throughout the process some reality which is in itself potential and indifferent to either actual state; and that, moreover, something which was actual disappears, while some new actuality appears, in this persisting potentiality. The abiding potential principle is called the _matter_ or _subject_ of the change; the transient actualizing principles are called _forms_. Not all these “forms” which precede or result from change are necessarily positive entities in themselves: they may be mere _privations_ of other forms (“_privatio_,” στέρησις): not all changes result in the acquisition of a new degree of positive actual being; some result in loss of perfection or actuality. Still, even in these cases, the state characterized by the less perfect degree of actuality has a determinate actual grade of being which is proper to itself, and which, as such, is not found actually, but only potentially, in the state characterized by the more perfect degree of actuality. When, then, a being changes from a more perfect to a less perfect state, the actuality of this less perfect state cannot be adequately accounted for by seeking it in the antecedent and more perfect state: it is not in this latter state _actually_, but only _potentially_; nor do we account for it by saying that it is “equivalently” in the greater actuality of the latter state: the two actualizing principles are really distinct, and neither is wholly or even partially the other. The significance of this consideration will appear presently in connection with the scholastic axiom: _Quidquid movetur ab alio movetur_.

Meanwhile we must guard against conceiving the potential or material factor in change as a sort of actual but hidden core of reality which itself persists unchanged throughout; and the formative or actualizing factors as superficially adorning this substratum by constantly replacing one another. Such a substitution of imagination images for intellectual thought will not help, but rather hinder, all accurate analysis. It is not the potential or material factor in things that changes, nor yet the actualizing or formal factors, but the things themselves; and if “things” are subject to “real change” it is manifest that this fact can be made intelligible, if at all, only by intellectually analysing the things and their changes into constitutive principles or factors which are nor themselves “things” or “changes”. Were we to arrive only at principles of the latter sort, so far from explaining anything we would really only have pushed back the problem a step farther. It may be that none of the attempts yet made by philosophers or scientists to offer an ultimate explanation of change is entirely satisfactory,—the scholastic explanation will be gradually outlined in these pages,—but it will be of advantage at least to recognize the shortcomings of theories that are certainly inadequate.

We are now in a position to state and explain the important scholastic aphorism embodying what has been called the Principle of Change (“_Principium Motus_”): _Quidquid movetur, ab alio movetur_: “Whatever undergoes change is changed by something else”. The term _motus_ is here taken in the wide sense of any real transition from potentiality to actuality, as is evident from the alternative statements of the same principle: _Nihil potest seipsum reducere e potentia in actum_: “Nothing can reduce itself from potentiality to actuality,” or, again, _Potentia, qua talis, nequit per semetipsam ad actum reduci, sed reducitur ab alio principio in actu_: “The potential as such cannot be reduced by itself to the actual, but only by some other already actual principle”.(77) This assertion, rightly understood, is self-evidently true; for the state of passive potentiality, as such, involves the absence of the correlative actuality in the potential subject; and since the actual, as such, involves a perfection which is not in the potential, the latter cannot confer upon itself this perfection: nothing can be the adequate principle or source of a perfection which is not in this principle or source: _nemo dat quod non habet_.

We have already anticipated the objection arising from the consideration that the state resulting from a change is sometimes in its totality less perfect than the state which existed prior to the change. Even in such cases there results from the change a new actuality which was not in the prior state, and which cannot be conceived as a mere part or residue of the latter, or regarded as equivalently contained in the latter. Even granting, as we must, that the net result of such a change is a loss of actuality or perfection in the subject of change, still there is always a gain which is not accounted for by the loss; there is always a new actual state which, as such, was not in the original state.

A more obvious objection to the principle arises from the consideration of vital action; but it is based on a misunderstanding of the principle under discussion. Living things, it is objected, move themselves: their _vital_ action is spontaneous and immanent: originating within themselves, it has its term too within themselves, resulting in their gradual development, growth, increase of actuality and perfection. Therefore it would appear that they move and perfect themselves; and hence the so-called “principle of change” is not true universally.

In reply to all this we admit that vital action is immanent, remaining within the agent to perfect the latter; also that it is spontaneous, inasmuch as when the agent is actually exercising vital functions it need not be actually undergoing the causal influence of any other created agent, or actually dependent on any such agent. But it must, nevertheless, in such action, be dependent on, and influenced by, _some actual being other than itself_. And the reason is obvious: If by such action it increases its own actual perfection, and becomes actually other than it was before such action, then it cannot have given itself the actuality of this perfection, which it possessed before only potentially. No doubt, it is not merely passively potential in regard to such actual perfections, as is the case in non-vital change which results in the subject from the transitive action of some outside cause upon the latter. The living thing has the active power of causing or producing in itself these actual perfections: there is interaction between its vital parts: through one organ or faculty it acts upon another, thus educing an actuality, a new perfection, in this other, and thus developing and perfecting its own being. But even considered as active it cannot be the adequate cause of the actuality acquired through the change. If this actuality is something _really_ over and above the reality of its active and passive potential principles, then it remains true that change implies the influence of an actual being other than the subject changed: _Quid quid movetur, ab alio movetur_.

The question here arises, not only in reference to vital agents, but to _all finite, created causes_: Does the active cause of change (together with the passive potentiality of the subject of change, whether this subject be the agent itself as in immanent activity, or something other than the agent as in transitive activity),—does this active power account _adequately_ for the new actuality educed in the change? It obviously does not; for the actuality acquired in the change is, as such, a new entity, a new perfection, in some degree positively surpassing the total reality of the combined active powers and passive potentialities which it replaces. In other words, if the actuality resulting from the change is not to be found in the immediate active and passive antecedents of the change, then we are inevitably referred, for an adequate explanation of this actuality, to some actual being above and beyond these antecedents. And to what sort of actual being are we referred? To a being in which the actuality of the effect resides only in the same way as it resides in the immediate active and passive antecedents of the change, that is _potentially_? No; for this would be useless, merely pushing the difficulty one step farther back. We are obliged rather to infer the existence of an Actual Being in whom the actuality of the said effect resides _actually_: not formally, of course, as it exists in itself when it is produced through the change; but eminently, _eminenter_, in such a way that its actualization outside Himself and under His influence does not involve in Him any loss of perfection, any increase of perfection, or any manner of change whatsoever. We are compelled in this way to infer, from the existence of change in the universe of our direct experience, the existence of a transcendent Immovable Prime Mover, a _Primum Movens Immobile_. All the active causes or principles of change which fall under our notice in the universe of direct experience are themselves subject to change. None of them causes change in any other thing without itself undergoing change. The active power of finite causes is itself finite. By educing the potentiality of other things into actuality they gradually use up their own energy; they diminish and lose their active power of producing effects: this belongs to the very nature of finite causes as such. Moreover, they are themselves passive as well as active; interaction is universal among the finite causes which constitute the universe of our direct experience: they all alike have passive potentiality and undergo change. Now, if any one finite cause in this system cannot adequately account for the new actuality evolved from the potential in any single process of change, neither can the whole system adequately account for it. What is true of them distributively is true of them taken all together when there is question of what belongs to their nature; and the fact that their active powers and passive potentialities _fall short_ of the actuality of the effects we attribute to them is a fact that appertains to their very nature as finite things. The phenomenon of continuous change in the universe involves the continuous appearance of _new actual being_. To account for this constant stream of actuality we are of necessity carried beyond the system of finite, changing being itself; we are forced to infer the existence of a source and principle which must itself be purely actual and exempt from all change—a Being who can cause all the actuality that results from change without losing or gaining or changing in any way Himself, because He possesses all finite actuality in Himself in a supereminent manner which transcends all the efforts of finite human intelligence to comprehend or characterize in any adequate or positive manner. The scholastics expressed this in the simple aphorism: _Omne novum ens est a Deo_. And it is the realization of this profound truth that underlies their teaching on the necessity of the Divine _Concursus_, _i.e._ the influence of the Infinite First Cause or Prime Mover permeating the efficiency of all finite or created causes. Here, for example, is a brief recent statement of that doctrine:—

“If we must admit a causal influence of these things [of direct experience] on one another, then a closer examination will convince us that a finite thing can never be the adequate cause of any effect, but is always, metaphysically regarded, only a part-cause, ever needing to be completed by another cause. Every effect is—at least under one aspect, at least as an effect—something new, something that was not there before. Even were the effect contained, whether formally or virtually, in the cause, it is certainly not identical with this latter, for if it were there would be no causality, nothing would ‘happen’. In all causing and happening, something which was heretofore only possible, becomes real and actual. But things cannot determine themselves to influence others, or to receive the influence of others, since they are not dependent in their being on one another. Hence the necessary inference that all being, all happening, all change, requires the concurrence of an Absolute Principle of being. When two things act on each other the Absolute Being must work in and with them, the same Absolute Being in both—to relate them to each other, and supplement their natural insufficiency.”

“Such is the profound teaching about the Divine Concursus with every creature.... God works in all and with all. He permeates all reality, everywhere; there is no being beyond Him or independent of His conserving and concurring power. Just as creatures are brought into being only through God’s omnipotence, and of themselves have no independent reality, so do they need the self-same ever-present, all-sustaining power to continue in this being and develop it by their activity. Every event in Nature is a transitory, passing phenomenon, so bound up with conditions and circumstances that it must disappear to give place to some other. How could a mode of being so incomplete discharge its function in existence without the concurrence of the First Cause?”(78)

We have seen now that _in the real order_ the potential presupposes the actual; for the potential cannot actualize itself, but can be actualized only by the action of some already actual being. Nor can we avoid this consequence by supposing the potential being to have had no actual beginning in time, but to be eternally in process of actualization; for even so, it must be eternally actualized _by some other actual being_—a position which Aristotle and some scholastics admit to be possible. Whether, then, we conceive the actualization as beginning in time or as proceeding from all eternity, it is self-contradictory to suppose the potential as capable of actualizing itself.

It is likewise true that the actual precedes the possible _in the order of our knowledge_. The concept of a thing as possible presupposes the concept of that thing as actual; for the possible is understood to be possible only by its intelligible relation to actual existence. This is evidently true of extrinsic possibility; but our knowledge even of the intrinsic possibility of a thing cannot be the first knowledge we possess in the order of time. Our first knowledge is of the actual; for the mind’s first cognitive act must have for object either itself or something not itself. But it knows itself as a consciously acting and therefore actual being. And it comes to know things other than itself only by the fact that such other things act upon it either immediately or mediately through sense-consciousness; so that in every hypothesis its first known object is something actual.(79)

The priority of the actual as compared with the potential in the real order, suggests a proof of the existence of God in the manner indicated above. It also affords a refutation of Hegelian monism. The conception of the world, including all the phenomena of mind and matter, as the gradual self-manifestation or evolution of a potential being eternally actualizing itself, is a self-contradictory conception. Scholastics rightly maintain that the realities from which we derive our first most abstract and transcendental notion of being in general, are actual realities. Hegelians seize on the object of this notion, identify it with pure thought, proclaim it the sole reality, and endow it with the power of becoming actually everything. It is manifest, therefore, that they endow purely potential being with the power of actualizing itself.

Nor can they fairly avoid this charge by pointing out that although their starting-point is not actual being (with which the scholastic philosophy of being commences), yet neither is it possible or potential being, but being which has neither of these determinations, being which abstracts from both, like the real being of the scholastics (7, 13). For though real being can be _an object of abstract human thought_ without either of the predicates “existent” or “non-existent,” yet it cannot be anything _in the real order_ without either of them. There it must be either actually existent or else merely potential. But Hegelians claim absolutely indeterminate being to be _as such_ something in the real order; and though they try to distinguish it from potential being they nevertheless think of it as potential being, for they distinctly and repeatedly declare that it can become all things, and does become all things, and is constantly, eternally transforming itself by an internal dialectic process into the phenomena which constitute the worlds of mind and matter. Contrasting it with the abstract “inert” being which they conceive to be the object of the traditional metaphysics, they endow “indeterminate being” with the active power of producing, and the passive potentiality of becoming, actually everything. Thus, in order to show _a priori_ how this indeterminate being must evolve itself by internal logical necessity into the world of our direct and immediate experience, they suppose it to be subject to change and to be at the same time self-actualizing, in direct opposition to the axiom that potential reality, reality which is subject to change, cannot actualize itself: _Quidquid movetur ab alio moveatur oportet_.

11. KINDS OF CHANGE.—Following Aristotle,(80) we may recognize a broad and clear distinction between four great classes of change (μεταβολή, _mutatio_) in the phenomena of our sense experience: local change (κίνησις κατὰ τόπον, φορά, _latio_); quantitative change (κατὰ τὸ πόσον, ἀύζησις ἤ φθίσις, _augmentatio vel diminutio_); qualitative change (κατὰ τὸ ποίον, ἀλλοίωσις, _alteratio_); and substantial change (κατ᾽ οὐσίαν, γένεσις ἤ φθορά). The three former are accidental, _i.e._ do not reach or affect the essence or substance of the thing that is changed; the fourth is substantial, a change of essence. Substantial change is regarded as taking place instantaneously, as soon as the condition brought about by the accidental changes leading up to it becomes naturally incompatible with the essence or nature of the subject. The accidental changes, on the other hand, are regarded as taking place gradually, as realizing and involving a succession of states or conditions in the subject. These changes, especially when they take place in corporeal things, are properly described as movement or motion (_motus_, _motio_). By movement or motion in the strict sense we therefore mean any change which takes place gradually or successively in a corporeal thing. It is only in a wider and improper sense that these terms are sometimes applied to activity of whatsoever kind, even of spiritual beings. In this sense we speak of thoughts, volitions, etc., as movements of the soul, _motus animae_; or of God as the Prime Mover ever in motion, the _Primum Movens semper in motu_.

With local change in material things, as also with quantitative change, growth and diminution of quantity (mass and volume), everyone is perfectly familiar. From the earliest times, moreover, we find both in science and philosophy the conception of matter as composed of, and divisible into, ultimate particles, themselves supposed to admit of no further real division, and hence called _atoms_ (ἄ-τομος, τέμνω). From the days of Grecian atomism men have attempted to show that all change in the Universe is ultimately reducible to changes of place, order, spatial arrangement and collocation, of those hypothetical atomic factors. It has likewise been commonly assumed that change in mass is solely due to change in the number of those atoms, and change in volume (of the same mass) to the relative density or closeness with which the atoms aggregate together; though some have held—and it is certainly not inconceivable—that exactly the same material entity, an atom let us say, may be capable of _real_ contraction and expansion, and so of _real_ change of volume: as distinct from the _apparent_ contraction and expansion of bodies, a change which is supposed to be due to change of density, _i.e._ to decrease or increase in the dimensions of the pores or interstices between the smaller constituent parts or molecules. However this may be, the attempts to reduce all change in physical nature to mere _mechanical_ change _i.e._ to spatial motions of the masses (_molar_ motions), the molecules (_molecular_ motions), and the atoms or other ultimate components of matter (whether vibratory, undulatory, rotatory or translational motions), have never been satisfactory.

Qualitative change is wider than material change, for it includes changes in spiritual beings, _i.e._ in beings which are outside the category of quantity and have a mode of existence altogether different from the extensional, spatial existence which characterizes matter. When, for instance, the human mind acquires knowledge, it undergoes qualitative change. But matter, too, has qualities, and is subject to qualitative change. It is endowed with _active_ qualities, _i.e._ with powers, forces, energies, whereby it can not merely perform mechanical work by producing local changes in the distribution of its mass throughout space, but also produce physical and chemical changes which seem at least to be different in their nature from mere mechanical changes. It is likewise endowed with _passive_ qualities which appear to the senses to be of various kinds, differing from one another and from the mechanical or quantitative characteristics of size, shape, motion, rest, etc. While these latter are called “primary qualities” of bodies—because conceived to be more fundamental and more closely inherent in the real and objective nature of matter—or “common sensibles” (_sensibilia communia_), because perceptible by more than one of our external senses—the former are called “secondary qualities,” because conceived to be less characteristic of the real and objective nature of matter, and more largely subjective products of our own sentient cognitive activity—or “proper sensibles” (_sensibilia propria_), because each of them is apprehended by only one of our external senses: colour, sound, taste, odour, temperature, material state or texture (_e.g._ roughness, liquidity, softness, etc.). Now about all these perceived qualities and their changes the question has been raised: Are they, as such, _i.e._ as perceived by us, really in the material things or bodies which make up the physical universe, and really different in these bodies from the quantitative factors and motions of the latter? Or, as such, are they not rather partially or wholly subjective phenomena—products, at least in part, of our own sense perception, states of our own consciousness, having nothing really corresponding to them in the external matter of the universe beyond the quantitative, mechanical factors and motions whereby matter acts upon our faculties of sense cognition and produces these states of consciousness in us? This is a question of the first importance, the solution of which belongs to Epistemology. Aristotle would not allow that the objective material universe can be denuded, in the way just suggested, of qualities and qualitative change; and scholastic philosophers have always held the same general view. What we have to note here, however, in regard to the question is simply this, that even if the world of matter were thus simplified by transferring all qualitative change to the subjective domain of consciousness, the reality of qualitative change and all the problems arising from it would still persist. To transfer qualitative change from object to subject, from matter to mind, is certainly something very different from explaining it as reducible to quantitative or mechanical change. The simplification thus effected would be more apparent than real: it would be simplifying the world of matter by transferring its complexity to the world of mind. This consideration is one which is sometimes lost sight of by scientists who advance mechanical hypotheses as ultimate explanations of the nature and activities of the physical universe.

If all material things and processes could be ultimately analysed into configurations and local motions of space-occupying atoms, homogeneous in nature and differing only in size and shape, then each of these ultimate atomic factors would be itself exempt from intrinsic change as to its own essence and individuality. In this hypothesis there would be really no such thing as _substantial_ change. The collection of atoms would form an immutable core of material reality, wholly simple and ever actual. Such an hypothesis, however, is utterly inadequate as an explanation of the facts of life and consciousness. And even as an account of the processes of the inorganic universe it encounters insuperable difficulties. The common belief of men has always been that even in this domain of reality there are fundamentally different _kinds_ of matter, kinds which differ from one another not merely in the shape and size and configuration and arrangement of their ultimate _actual_ constituents, but even in the very substance or nature of these constituents; and that there are some material changes which affect the actual substance itself of the matter which undergoes them. This belief scholastics, again following Aristotle, hold to be a correct belief, and one which is well grounded in reason. And this belief in turn involves the view that every type of actual material entity—whether merely inorganic, or endowed with life, or even allied with a higher, spiritual mode of being as in the case of man himself—is _essentially composite_, essentially a synthesis of _potential_ and _actual_ principles of being, and therefore capable of _substantial_ change. The actually existing material being scholastics describe as _materia secunda_, the ὕλη ἐσχάτη of Aristotle; the purely potential factor, which is actualized in this or that particular kind of matter, they describe as _materia prima_, the ὕλη πρώτη of Aristotle; the actualizing, specifying, formative principle, they designate as _forma substantialis_ (εἶδος). And since the purely potential principle cannot actually exist except as actualized by some formative principle, all substantial change or transition from one substantial type to another is necessarily both a _corruptio_ and a _generatio_. That is, it involves the actual disappearance of one substantial form and the actual appearance of another. Hence the scholastic aphorism regarding substantial change: _Corruptio unius est generatio alterius_: the corruption or destruction of one kind of material thing involves the generation of another kind.

The concepts of _materia prima_ and _forma substantialis_ are concepts not of phenomenal entities directly accessible to the senses or the imagination, but of principles which can be reached only mediately and by intellect proper. They cannot be pictured in the imagination, which can only attain to the sensible. We may help ourselves to grasp them intellectually by the analogy of the shapeless block of marble and the figure educed therefrom by the sculptor, but this is only an analogy: just as the statue results from the union of an _accidental_ form with an existing matter, so this matter itself, the substance _marble_, is composed of a _substantial_ form and a primordial, _potential_ matter. But there the analogy ceases.

Furthermore, when we consider that the proper and primary objects of the human intellect itself are corporeal things or bodies, and that these bodies actually exist in nature only as composite substances, subject to essential or substantial change, we shall realize why it is that the concept of _materia prima_ especially, being a mediate and negative concept, is so difficult to grasp; for, as the scholastics describe it, translating Aristotle’s formula, it is in itself _neque quid, neque quantum, neque quale, neque aliquid eorum quibus ens determinatur_.(81) But it is through intellectual concepts alone, and not through imagination images, that we may hope to analyse the nature and processes even of the world of corporeal reality; and, as St. Thomas well observes, it was because the ancient Greek atomists did not rise above the level of thinking in imagination images that they failed to recognize the existence, or explain the nature, of substantial change in the material universe(82): an observation which applies with equal force to those scientists and philosophers of our own time who would fain reduce all physical processes to mere mechanical change.

Those, then, are the principal kinds of change, as analysed by Aristotle and the scholastics. We may note, finally, that the distinction between _immanent_ and _transitive_ activity is also applied to change—that is, to change considered as a process, not to the result of the change, to change _in fieri_, not _in facto esse_. Immanent movement or activity (_motio_, _actio immanens_) is that of which the term, the educed actuality, remains within the agent—which latter is therefore at once both _agens_ and _patiens_. Vital action is of this kind. Transitive movement or activity, on the other hand (_motio_, _actio transiens_), is that of which the term is some actuality educed in a being other than the agent. The _patiens_ is here really distinct from the _agens_; and it is in the former, not in the latter, that the change takes place: _actio fit in passo_. All change in the inorganic universe is of this sort (101).