Summa Th. I EN Qu.7 a.3
Objection: 1. It seems that there can be something actually infinite in magnitude. For in mathematics there is no error, since "there is no lie in things abstract," as the Philosopher says (Phys. ii). But mathematics uses the infinite in magnitude; thus, the geometrician in his demonstrations says, "Let this line be infinite." Therefore it is not impossible for a thing to be infinite in magnitude.
2. Further, what is not against the nature of anything, can agree with it. Now to be infinite is not against the nature of magnitude; but rather both the finite and the infinite seem to be properties of quantity. Therefore it is not impossible for some magnitude to be infinite.
3. Further, magnitude is infinitely divisible, for the continuous is defined that which is infinitely divisible, as is clear from Phys. iii. But contraries are concerned about one and the same thing. Since therefore addition is opposed to division, and increase opposed to diminution, it appears that magnitude can be increased to infinity. Therefore it is possible for magnitude to be infinite.
4. Further, movement and time have quantity and continuity derived from the magnitude over which movement passes, as is said in Phys. iv. But it is not against the nature of time and movement to be infinite, since every determinate indivisible in time and circular movement is both a beginning and an end. Therefore neither is it against the nature of magnitude to be infinite.
On the contrary Every body has a surface. But every body which has a surface is finite; because surface is the term of a finite body. Therefore all bodies are finite. The same applies both to surface and to a line. Therefore nothing is infinite in magnitude.
I answer that It is one thing to be infinite in essence, and another to be infinite in magnitude. For granted that a body exists infinite in magnitude, as fire or air, yet this could not be infinite in essence, because its essence would be terminated in a species by its form, and confined to individuality by matter. And so assuming from these premises that no creature is infinite in essence, it still remains to inquire whether any creature can be infinite in magnitude.
We must therefore observe that a body, which is a complete magnitude, can be considered in two ways; mathematically, in respect to its quantity only; and naturally, as regards its matter and form.
Now it is manifest that a natural body cannot be actually infinite. For every natural body has some determined substantial form. Since therefore the accidents follow upon the substantial form, it is necessary that determinate accidents should follow upon a determinate form; and among these accidents is quantity. So every natural body has a greater or smaller determinate quantity. Hence it is impossible for a natural body to be infinite. The same appears from movement; because every natural body has some natural movement; whereas an infinite body could not have any natural movement; neither direct, because nothing moves naturally by a direct movement unless it is out of its place; and this could not happen to an infinite body, for it would occupy every place, and thus every place would be indifferently its own place. Neither could it move circularly; forasmuch as circular motion requires that one part of the body is necessarily transferred to a place occupied by another part, and this could not happen as regards an infinite circular body: for if two lines be drawn from the centre, the farther they extend from the centre, the farther they are from each other; therefore, if a body were infinite, the lines would be infinitely distant from each other; and thus one could never occupy the place belonging to any other.
The same applies to a mathematical body. For if we imagine a mathematical body actually existing, we must imagine it under some form, because nothing is actual except by its form; hence, since the form of quantity as such is figure, such a body must have some figure, and so would be finite; for figure is confined by a term or boundary.
Reply to Objection: 1. A geometrician does not need to assume a line actually infinite, but takes some actually finite line, from which he subtracts whatever he finds necessary; which line he calls infinite.
2. Although the infinite is not against the nature of magnitude in general, still it is against the nature of any species of it; thus, for instance, it is against the nature of a bicubical or tricubical magnitude, whether circular or triangular, and so on. Now what is not possible in any species cannot exist in the genus; hence there cannot be any infinite magnitude, since no species of magnitude is infinite.
3. The infinite in quantity, as was shown above, belongs to matter. Now by division of the whole we approach to matter, forasmuch as parts have the aspect of matter; but by addition we approach to the whole which has the aspect of a form. Therefore the infinite is not in the addition of magnitude, but only in division.
4. Movement and time are whole, not actually but successively; hence they have potentiality mixed with actuality. But magnitude is an actual whole; therefore the infinite in quantity refers to matter, and does not agree with the totality of magnitude; yet it agrees with the totality of time and movement: for it is proper to matter to be in potentiality.
Objection: 1. It seems that an actually infinite multitude is possible. For it is not impossible for a potentiality to be made actual. But number can be multiplied to infinity. Therefore it is possible for an infinite multitude actually to exist.
2. Further, it is possible for any individual of any species to be made actual. But the species of figures are infinite. Therefore an infinite number of actual figures is possible.
3. Further, things not opposed to each other do not obstruct each other. But supposing a multitude of things to exist, there can still be many others not opposed to them. Therefore it is not impossible for others also to coexist with them, and so on to infinitude; therefore an actual infinite number of things is possible.
On the contrary It is written, "Thou hast ordered all things in measure, and number, and weight" (Sg 11,21).
I answer that A twofold opinion exists on this subject. Some, as Avicenna and Algazel, said that it was impossible for an actually infinite multitude to exist absolutely; but that an accidentally infinite multitude was not impossible. A multitude is said to be infinite absolutely, when an infinite multitude is necessary that something may exist. Now this is impossible; because it would entail something dependent on an infinity for its existence; and hence its generation could never come to be, because it is impossible to pass through an infinite medium.
A multitude is said to be accidentally infinite when its existence as such is not necessary, but accidental. This can be shown, for example, in the work of a carpenter requiring a certain absolute multitude; namely, art in the soul, the movement of the hand, and a hammer; and supposing that such things were infinitely multiplied, the carpentering work would never be finished, forasmuch as it would depend on an infinite number of causes. But the multitude of hammers, inasmuch as one may be broken and another used, is an accidental multitude; for it happens by accident that many hammers are used, and it matters little whether one or two, or many are used, or an infinite number, if the work is carried on for an infinite time. In this way they said that there can be an accidentally infinite multitude.
This, however, is impossible; since every kind of multitude must belong to a species of multitude. Now the species of multitude are to be reckoned by the species of numbers. But no species of number is infinite; for every number is multitude measured by one. Hence it is impossible for there to be an actually infinite multitude, either absolute or accidental. Likewise multitude in nature is created; and everything created is comprehended under some clear intention of the Creator; for no agent acts aimlessly. Hence everything created must be comprehended in a certain number. Therefore it is impossible for an actually infinite multitude to exist, even accidentally. But a potentially infinite multitude is possible; because the increase of multitude follows upon the division of magnitude; since the more a thing is divided, the greater number of things result. Hence, as the infinite is to be found potentially in the division of the continuous, because we thus approach matter, as was shown in the preceding article, by the same rule, the infinite can be also found potentially in the addition of multitude.
Reply to Objection: 1. Every potentiality is made actual according to its mode of being; for instance, a day is reduced to act successively, and not all at once. Likewise the infinite in multitude is reduced to act successively, and not all at once; because every multitude can be succeeded by another multitude to infinity.
2. Species of figures are infinite by infinitude of number. Now there are various species of figures, such as trilateral, quadrilateral and so on; and as an infinitely numerable multitude is not all at once reduced to act, so neither is the multitude of figures.
3. Although the supposition of some things does not preclude the supposition of others, still the supposition of an infinite number is opposed to any single species of multitude. Hence it is not possible for an actually infinite multitude to exist.
Since it evidently belongs to the infinite to be present everywhere, and in all things, we now consider whether this belongs to God; and concerning this there arise four points of inquiry:
(1) Whether God is in all things?
(2) Whether God is everywhere?
(3) Whether God is everywhere by essence, power, and presence?
(4) Whether to be everywhere belongs to God alone?
Objection: 1. It seems that God is not in all things. For what is above all things is not in all things. But God is above all, according to the Psalm (Ps 112,4), "The Lord is high above all nations," etc. Therefore God is not in all things.
2. Further, what is in anything is thereby contained. Now God is not contained by things, but rather does He contain them. Therefore God is not in things but things are rather in Him. Hence Augustine says (Octog. Tri. Quaest. qu. 20), that "in Him things are, rather than He is in any place."
3. Further, the more powerful an agent is, the more extended is its action. But God is the most powerful of all agents. Therefore His action can extend to things which are far removed from Him; nor is it necessary that He should be in all things.
4. Further, the demons are beings. But God is not in the demons; for there is no fellowship between light and darkness (2Co 6,14). Therefore God is not in all things.
On the contrary A thing is wherever it operates. But God operates in all things, according to Is 26,12, "Lord . . . Thou hast wrought all our works in [Vulg.: 'for'] us." Therefore God is in all things.
I answer that God is in all things; not, indeed, as part of their essence, nor as an accident, but as an agent is present to that upon which it works. For an agent must be joined to that wherein it acts immediately and touch it by its power; hence it is proved in Phys. vii that the thing moved and the mover must be joined together. Now since God is very being by His own essence, created being must be His proper effect; as to ignite is the proper effect of fire. Now God causes this effect in things not only when they first begin to be, but as long as they are preserved in being; as light is caused in the air by the sun as long as the air remains illuminated. Therefore as long as a thing has being, God must be present to it, according to its mode of being. But being is innermost in each thing and most fundamentally inherent in all things since it is formal in respect of everything found in a thing, as was shown above (Question [7], Article [1]). Hence it must be that God is in all things, and innermostly.
Reply to Objection: 1. God is above all things by the excellence of His nature; nevertheless, He is in all things as the cause of the being of all things; as was shown above in this article.
2. Although corporeal things are said to be in another as in that which contains them, nevertheless, spiritual things contain those things in which they are; as the soul contains the body. Hence also God is in things containing them; nevertheless, by a certain similitude to corporeal things, it is said that all things are in God; inasmuch as they are contained by Him.
3. No action of an agent, however powerful it may be, acts at a distance, except through a medium. But it belongs to the great power of God that He acts immediately in all things. Hence nothing is distant from Him, as if it could be without God in itself. But things are said to be distant from God by the unlikeness to Him in nature or grace; as also He is above all by the excellence of His own nature.
4. In the demons there is their nature which is from God, and also the deformity of sin which is not from Him; therefore, it is not to be absolutely conceded that God is in the demons, except with the addition, "inasmuch as they are beings." But in things not deformed in their nature, we must say absolutely that God is.
Objection: 1. It seems that God is not everywhere. For to be everywhere means to be in every place. But to be in every place does not belong to God, to Whom it does not belong to be in place at all; for "incorporeal things," as Boethius says (De Hebdom.), "are not in a place." Therefore God is not everywhere.
2. Further, the relation of time to succession is the same as the relation of place to permanence. But one indivisible part of action or movement cannot exist in different times; therefore neither can one indivisible part in the genus of permanent things be in every place. Now the divine being is not successive but permanent. Therefore God is not in many places; and thus He is not everywhere.
3. Further, what is wholly in any one place is not in part elsewhere. But if God is in any one place He is all there; for He has no parts. No part of Him then is elsewhere; and therefore God is not everywhere.
On the contrary It is written, "I fill heaven and earth." (Jr 23,24).
I answer that Since place is a thing, to be in place can be understood in a twofold sense; either by way of other things---i.e. as one thing is said to be in another no matter how; and thus the accidents of a place are in place; or by a way proper to place; and thus things placed are in a place. Now in both these senses, in some way God is in every place; and this is to be everywhere. First, as He is in all things giving them being, power and operation; so He is in every place as giving it existence and locative power. Again, things placed are in place, inasmuch as they fill place; and God fills every place; not, indeed, like a body, for a body is said to fill place inasmuch as it excludes the co-presence of another body; whereas by God being in a place, others are not thereby excluded from it; indeed, by the very fact that He gives being to the things that fill every place, He Himself fills every place.
Reply to Objection: 1. Incorporeal things are in place not by contact of dimensive quantity, as bodies are but by contact of power.
2. The indivisible is twofold. One is the term of the continuous; as a point in permanent things, and as a moment in succession; and this kind of the indivisible in permanent things, forasmuch as it has a determinate site, cannot be in many parts of place, or in many places; likewise the indivisible of action or movement, forasmuch as it has a determinate order in movement or action, cannot be in many parts of time. Another kind of the indivisible is outside of the whole genus of the continuous; and in this way incorporeal substances, like God, angel and soul, are called indivisible. Such a kind of indivisible does not belong to the continuous, as a part of it, but as touching it by its power; hence, according as its power can extend itself to one or to many, to a small thing, or to a great one, in this way it is in one or in many places, and in a small or large place.
3. A whole is so called with reference to its parts. Now part is twofold: viz. a part of the essence, as the form and the matter are called parts of the composite, while genus and difference are called parts of species. There is also part of quantity into which any quantity is divided. What therefore is whole in any place by totality of quantity, cannot be outside of that place, because the quantity of anything placed is commensurate to the quantity of the place; and hence there is no totality of quantity without totality of place. But totality of essence is not commensurate to the totality of place. Hence it is not necessary for that which is whole by totality of essence in a thing, not to be at all outside of it. This appears also in accidental forms which have accidental quantity; as an example, whiteness is whole in each part of the surface if we speak of its totality of essence; because according to the perfect idea of its species it is found to exist in every part of the surface. But if its totality be considered according to quantity which it has accidentally, then it is not whole in every part of the surface. On the other hand, incorporeal substances have no totality either of themselves or accidentally, except in reference to the perfect idea of their essence. Hence, as the soul is whole in every part of the body, so is God whole in all things and in each one.
Objection: 1. It seems that the mode of God's existence in all things is not properly described by way of essence, presence and power. For what is by essence in anything, is in it essentially. But God is not essentially in things; for He does not belong to the essence of anything. Therefore it ought not to be said that God is in things by essence, presence and power.
2. Further, to be present in anything means not to be absent from it. Now this is the meaning of God being in things by His essence, that He is not absent from anything. Therefore the presence of God in all things by essence and presence means the same thing. Therefore it is superfluous to say that God is present in things by His essence, presence and power.
3. Further, as God by His power is the principle of all things, so He is the same likewise by His knowledge and will. But it is not said that He is in things by knowledge and will. Therefore neither is He present by His power.
4. Further, as grace is a perfection added to the substance of a thing, so many other perfections are likewise added. Therefore if God is said to be in certain persons in a special way by grace, it seems that according to every perfection there ought to be a special mode of God's existence in things.
On the contrary A gloss on the Canticle of Canticles (5) says that, "God by a common mode is in all things by His presence, power and substance; still He is said to be present more familiarly in some by grace" [*The quotation is from St. Gregory, (Hom. viii in Ezech.)].
I answer that God is said to be in a thing in two ways; in one way after the manner of an efficient cause; and thus He is in all things created by Him; in another way he is in things as the object of operation is in the operator; and this is proper to the operations of the soul, according as the thing known is in the one who knows; and the thing desired in the one desiring. In this second way God is especially in the rational creature which knows and loves Him actually or habitually. And because the rational creature possesses this prerogative by grace, as will be shown later (Question [12]). He is said to be thus in the saints by grace.
But how He is in other things created by Him, may be considered from human affairs. A king, for example, is said to be in the whole kingdom by his power, although he is not everywhere present. Again a thing is said to be by its presence in other things which are subject to its inspection; as things in a house are said to be present to anyone, who nevertheless may not be in substance in every part of the house. Lastly, a thing is said to be by way of substance or essence in that place in which its substance may be. Now there were some (the Manichees) who said that spiritual and incorporeal things were subject to the divine power; but that visible and corporeal things were subject to the power of a contrary principle. Therefore against these it is necessary to say that God is in all things by His power.
But others, though they believed that all things were subject to the divine power, still did not allow that divine providence extended to these inferior bodies, and in the person of these it is said, "He walketh about the poles of the heavens; and He doth not consider our things [*Vulg.: 'He doth not consider . . . and He walketh,' etc.]" (Jb 22,14). Against these it is necessary to say that God is in all things by His presence.
Further, others said that, although all things are subject to God's providence, still all things are not immediately created by God; but that He immediately created the first creatures, and these created the others. Against these it is necessary to say that He is in all things by His essence.
Therefore, God is in all things by His power, inasmuch as all things are subject to His power; He is by His presence in all things, as all things are bare and open to His eyes; He is in all things by His essence, inasmuch as He is present to all as the cause of their being.
Reply to Objection: 1. God is said to be in all things by essence, not indeed by the essence of the things themselves, as if He were of their essence; but by His own essence; because His substance is present to all things as the cause of their being.
2. A thing can be said to be present to another, when in its sight, though the thing may be distant in substance, as was shown in this article; and therefore two modes of presence are necessary; viz. by essence and by presence.
3. Knowledge and will require that the thing known should be in the one who knows, and the thing willed in the one who wills. Hence by knowledge and will things are more truly in God than God in things. But power is the principle of acting on another; hence by power the agent is related and applied to an external thing; thus by power an agent may be said to be present to another.
4. No other perfection, except grace, added to substance, renders God present in anything as the object known and loved; therefore only grace constitutes a special mode of God's existence in things. There is, however, another special mode of God's existence in man by union, which will be treated of in its own place (TP).
Objection: 1. It seems that to be everywhere does not belong to God alone. For the universal, according to the Philosopher (Poster. i), is everywhere, and always; primary matter also, since it is in all bodies, is everywhere. But neither of these is God, as appears from what is said above (Question [3]). Therefore to be everywhere does not belong to God alone.
2. Further, number is in things numbered. But the whole universe is constituted in number, as appears from the Book of Wisdom (Sg 11,21). Therefore there is some number which is in the whole universe, and is thus everywhere.
3. Further, the universe is a kind of "whole perfect body" (Coel. et Mund. i). But the whole universe is everywhere, because there is no place outside it. Therefore to be everywhere does not belong to God alone.
4. Further, if any body were infinite, no place would exist outside of it, and so it would be everywhere. Therefore to be everywhere does not appear to belong to God alone.
5. Further, the soul, as Augustine says (De Trin. vi, 6), is "whole in the whole body, and whole in every one of its parts." Therefore if there was only one animal in the world, its soul would be everywhere; and thus to be everywhere does not belong to God alone.
6. Further, as Augustine says (Ep 137), "The soul feels where it sees, and lives where it feels, and is where it lives." But the soul sees as it were everywhere: for in a succession of glances it comprehends the entire space of the heavens in its sight. Therefore the soul is everywhere.
On the contrary Ambrose says (De Spir. Sanct. i, 7): "Who dares to call the Holy Ghost a creature, Who in all things, and everywhere, and always is, which assuredly belongs to the divinity alone?"
I answer that To be everywhere primarily and absolutely, is proper to God. Now to be everywhere primarily is said of that which in its whole self is everywhere; for if a thing were everywhere according to its parts in different places, it would not be primarily everywhere, forasmuch as what belongs to anything according to part does not belong to it primarily; thus if a man has white teeth, whiteness belongs primarily not to the man but to his teeth. But a thing is everywhere absolutely when it does not belong to it to be everywhere accidentally, that is, merely on some supposition; as a grain of millet would be everywhere, supposing that no other body existed. It belongs therefore to a thing to be everywhere absolutely when, on any supposition, it must be everywhere; and this properly belongs to God alone. For whatever number of places be supposed, even if an infinite number be supposed besides what already exist, it would be necessary that God should be in all of them; for nothing can exist except by Him. Therefore to be everywhere primarily and absolutely belongs to God and is proper to Him: because whatever number of places be supposed to exist, God must be in all of them, not as to a part of Him, but as to His very self.
Reply to Objection: 1. The universal, and also primary matter are indeed everywhere; but not according to the same mode of existence.
2. Number, since it is an accident, does not, of itself, exist in place, but accidentally; neither is the whole but only part of it in each of the things numbered; hence it does not follow that it is primarily and absolutely everywhere.
3. The whole body of the universe is everywhere, but not primarily; forasmuch as it is not wholly in each place, but according to its parts; nor again is it everywhere absolutely, because, supposing that other places existed besides itself, it would not be in them.
4. If an infinite body existed, it would be everywhere; but according to its parts.
5. Were there one animal only, its soul would be everywhere primarily indeed, but only accidentally.
6. When it is said that the soul sees anywhere, this can be taken in two senses. In one sense the adverb "anywhere" determines the act of seeing on the part of the object; and in this sense it is true that while it sees the heavens, it sees in the heavens; and in the same way it feels in the heavens; but it does not follow that it lives or exists in the heavens, because to live and to exist do not import an act passing to an exterior object. In another sense it can be understood according as the adverb determines the act of the seer, as proceeding from the seer; and thus it is true that where the soul feels and sees, there it is, and there it lives according to this mode of speaking; and thus it does not follow that it is everywhere.
We next consider God's immutability, and His eternity following on His immutability. On the immutability of God there are two points of inquiry:
(1) Whether God is altogether immutable?
(2) Whether to be immutable belongs to God alone?
Objection: 1. It seems that God is not altogether immutable. For whatever moves itself is in some way mutable. But, as Augustine says (Gn ad lit viii, 20), "The Creator Spirit moves Himself neither by time, nor by place." Therefore God is in some way mutable.
2. Further, it is said of Wisdom, that "it is more mobile than all things active [Vulg.'mobilior']" (Sg 7,24). But God is wisdom itself; therefore God is movable.
3. Further, to approach and to recede signify movement. But these are said of God in Scripture, "Draw nigh to God and He will draw nigh to you" (Jc 4,8). Therefore God is mutable.
On the contrary It is written, "I am the Lord, and I change not" (Ml 3,6).
I answer that From what precedes, it is shown that God is altogether immutable.
1. First, because it was shown above that there is some first being, whom we call God; and that this first being must be pure act, without the admixture of any potentiality, for the reason that, absolutely, potentiality is posterior to act. Now everything which is in any way changed, is in some way in potentiality. Hence it is evident that it is impossible for God to be in any way changeable.
2. Secondly, because everything which is moved, remains as it was in part, and passes away in part; as what is moved from whiteness to blackness, remains the same as to substance; thus in everything which is moved, there is some kind of composition to be found. But it has been shown above (Question [3], Article [7]) that in God there is no composition, for He is altogether simple. Hence it is manifest that God cannot be moved.
3. Thirdly, because everything which is moved acquires something by its movement, and attains to what it had not attained previously. But since God is infinite, comprehending in Himself all the plenitude of perfection of all being, He cannot acquire anything new, nor extend Himself to anything whereto He was not extended previously. Hence movement in no way belongs to Him. So, some of the ancients, constrained, as it were, by the truth, decided that the first principle was immovable.
Reply to Objection: 1. Augustine there speaks in a similar way to Plato, who said that the first mover moves Himself; calling every operation a movement, even as the acts of understanding, and willing, and loving, are called movements. Therefore because God understands and loves Himself, in that respect they said that God moves Himself, not, however, as movement and change belong to a thing existing in potentiality, as we now speak of change and movement.
2. Wisdom is called mobile by way of similitude, according as it diffuses its likeness even to the outermost of things; for nothing can exist which does not proceed from the divine wisdom by way of some kind of imitation, as from the first effective and formal principle; as also works of art proceed from the wisdom of the artist. And so in the same way, inasmuch as the similitude of the divine wisdom proceeds in degrees from the highest things, which participate more fully of its likeness, to the lowest things which participate of it in a lesser degree, there is said to be a kind of procession and movement of the divine wisdom to things; as when we say that the sun proceeds to the earth, inasmuch as the ray of light touches the earth. In this way Dionysius (Coel. Hier. i) expounds the matter, that every procession of the divine manifestation comes to us from the movement of the Father of light.
3. These things are said of God in Scripture metaphorically. For as the sun is said to enter a house, or to go out, according as its rays reach the house, so God is said to approach to us, or to recede from us, when we receive the influx of His goodness, or decline from Him.
Objection: 1. It seems that to be immutable does not belong to God alone. For the Philosopher says (Metaph. ii) that "matter is in everything which is moved." But, according to some, certain created substances, as angels and souls, have not matter. Therefore to be immutable does not belong to God alone.
2.: Further, everything in motion moves to some end. What therefore has already attained its ultimate end, is not in motion. But some creatures have already attained to their ultimate end; as all the blessed in heaven. Therefore some creatures are immovable.
3. Further, everything which is mutable is variable. But forms are invariable; for it is said (Sex Princip. i) that "form is essence consisting of the simple and invariable." Therefore it does not belong to God alone to be immutable.
On the contrary Augustine says (De Nat. Boni. i), "God alone is immutable; and whatever things He has made, being from nothing, are mutable."
I answer that God alone is altogether immutable; whereas every creature is in some way mutable. Be it known therefore that a mutable thing can be called so in two ways: by a power in itself; and by a power possessed by another. For all creatures before they existed, were possible, not by any created power, since no creature is eternal, but by the divine power alone, inasmuch as God could produce them into existence. Thus, as the production of a thing into existence depends on the will of God, so likewise it depends on His will that things should be preserved; for He does not preserve them otherwise than by ever giving them existence; hence if He took away His action from them, all things would be reduced to nothing, as appears from Augustine (Gn ad lit. iv, 12). Therefore as it was in the Creator's power to produce them before they existed in themselves, so likewise it is in the Creator's power when they exist in themselves to bring them to nothing. In this way therefore, by the power of another---namely, of God---they are mutable, inasmuch as they are producible from nothing by Him, and are by Him reducible from existence to non-existence.
If, however, a thing is called mutable by a power in itself, thus also in some manner every creature is mutable. For every creature has a twofold power, active and passive; and I call that power passive which enables anything to attain its perfection either in being, or in attaining to its end. Now if the mutability of a thing be considered according to its power for being, in that way all creatures are not mutable, but those only in which what is potential in them is consistent with non-being. Hence, in the inferior bodies there is mutability both as regards substantial being, inasmuch as their matter can exist with privation of their substantial form, and also as regards their accidental being, supposing the subject to coexist with privation of accident; as, for example, this subject "man" can exist with "not-whiteness" and can therefore be changed from white to not-white. But supposing the accident to be such as to follow on the essential principles of the subject, then the privation of such an accident cannot coexist with the subject. Hence the subject cannot be changed as regards that kind of accident; as, for example, snow cannot be made black. Now in the celestial bodies matter is not consistent with privation of form, because the form perfects the whole potentiality of the matter; therefore these bodies are not mutable as to substantial being, but only as to locality, because the subject is consistent with privation of this or that place. On the other hand incorporeal substances, being subsistent forms which, although with respect to their own existence are as potentiality to act, are not consistent with the privation of this act; forasmuch as existence is consequent upon form, and nothing corrupts except it lose its form. Hence in the form itself there is no power to non-existence; and so these kinds of substances are immutable and invariable as regards their existence. Wherefore Dionysius says (Div. Nom. iv) that "intellectual created substances are pure from generation and from every variation, as also are incorporeal and immaterial substances." Still, there remains in them a twofold mutability: one as regards their potentiality to their end; and in that way there is in them a mutability according to choice from good to evil, as Damascene says (De Fide ii, 3,4); the other as regards place, inasmuch as by their finite power they attain to certain fresh places---which cannot be said of God, who by His infinity fills all places, as was shown above (Question [8], Article [2]).
Thus in every creature there is a potentiality to change either as regards substantial being as in the case of things corruptible; or as regards locality only, as in the case of the celestial bodies; or as regards the order to their end, and the application of their powers to divers objects, as in the case with the angels; and universally all creatures generally are mutable by the power of the Creator, in Whose power is their existence and non-existence. Hence since God is in none of these ways mutable, it belongs to Him alone to be altogether immutable.
Reply to Objection: 1. This objection proceeds from mutability as regards substantial or accidental being; for philosophers treated of such movement.
2. The good angels, besides their natural endowment of immutability of being, have also immutability of election by divine power; nevertheless there remains in them mutability as regards place.
3. Forms are called invariable, forasmuch as they cannot be subjects of variation; but they are subject to variation because by them their subject is variable. Hence it is clear that they vary in so far as they are; for they are not called beings as though they were the subject of being, but because through them something has being.
Summa Th. I EN Qu.7 a.3