Summa Theologica, by St. Thomas Aquinas, [1947], at sacred-texts.com
When the existence of a thing has been ascertained there remains the further question of the manner of its existence, in order that we may know its essence. Now, because we cannot know what God is, but rather what He is not, we have no means for considering how God is, but rather how He is not.
Therefore, we must consider: (1) How He is not; (2) How He is known by us; (3) How He is named.
Now it can be shown how God is not, by denying Him whatever is opposed to the idea of Him, viz. composition, motion, and the like. Therefore (1) we must discuss His simplicity, whereby we deny composition in Him; and because whatever is simple in material things is imperfect and a part of something else, we shall discuss (2) His perfection; (3) His infinity; (4) His immutability; (5) His unity.
Concerning His simplicity, there are eight points of inquiry:
(1) Whether God is a body?
(2) Whether He is composed of matter and form?
(3) Whether in Him there is composition of quiddity, essence or nature, and subject?
(4) Whether He is composed of essence and existence?
(5) Whether He is composed of genus and difference?
(6) Whether He is composed of subject and accident?
(7) Whether He is in any way composite, or wholly simple?
(8) Whether He enters into composition with other things?
Objection 1: It seems that God is a body. For a body is that which has the three dimensions. But Holy Scripture attributes the three dimensions to God, for it is written: "He is higher than Heaven, and what wilt thou do? He is deeper than Hell, and how wilt thou know? The measure of Him is longer than the earth and broader than the sea" (Job 11:8, 9). Therefore God is a body.
Objection 2: Further, everything that has figure is a body, since figure is a quality of quantity. But God seems to have figure, for it is written: "Let us make man to our image and likeness" (Gn. 1:26). Now a figure is called an image, according to the text: "Who being the brightness of His glory and the figure," i.e. the image, "of His substance" (Heb. 1:3). Therefore God is a body.
Objection 3: Further, whatever has corporeal parts is a body. Now Scripture attributes corporeal parts to God. "Hast thou an arm like God?" (Job 40:4); and "The eyes of the Lord are upon the just" (Ps. 33:16); and "The right hand of the Lord hath wrought strength" (Ps. 117:16). Therefore God is a body.
Objection 4: Further, posture belongs only to bodies. But something which supposes posture is said of God in the Scriptures: "I saw the Lord sitting" (Is. 6:1), and "He standeth up to judge" (Is. 3:13). Therefore God is a body.
Objection 5: Further, only bodies or things corporeal can be a local term "wherefrom" or "whereto." But in the Scriptures God is spoken of as a local term "whereto," according to the words, "Come ye to Him and be enlightened" (Ps. 33:6), and as a term "wherefrom": "All they that depart from Thee shall be written in the earth" (Jer. 17:13). Therefore God is a body.
On the contrary, It is written in the Gospel of St. John (Jn. 4:24): "God is a spirit."
I answer that, It is absolutely true that God is not a body; and this can be shown in three ways. First, because no body is in motion unless it be put in motion, as is evident from induction. Now it has been already proved (Q[2], A[3]), that God is the First Mover, and is Himself unmoved. Therefore it is clear that God is not a body. Secondly, because the first being must of necessity be in act, and in no way in potentiality. For although in any single thing that passes from potentiality to actuality, the potentiality is prior in time to the actuality; nevertheless, absolutely speaking, actuality is prior to potentiality; for whatever is in potentiality can be reduced into actuality only by some being in actuality. Now it has been already proved that God is the First Being. It is therefore impossible that in God there should be any potentiality. But every body is in potentiality because the continuous, as such, is divisible to infinity; it is therefore impossible that God should be a body. Thirdly, because God is the most noble of beings. Now it is impossible for a body to be the most noble of beings; for a body must be either animate or inanimate; and an animate body is manifestly nobler than any inanimate body. But an animate body is not animate precisely as body; otherwise all bodies would be animate. Therefore its animation depends upon some other thing, as our body depends for its animation on the soul. Hence that by which a body becomes animated must be nobler than the body. Therefore it is impossible that God should be a body.
Reply to Objection 1: As we have said above (Q[1], A[9]), Holy Writ puts before us spiritual and divine things under the comparison of corporeal things. Hence, when it attributes to God the three dimensions under the comparison of corporeal quantity, it implies His virtual quantity; thus, by depth, it signifies His power of knowing hidden things; by height, the transcendence of His excelling power; by length, the duration of His existence; by breadth, His act of love for all. Or, as says Dionysius (Div. Nom. ix), by the depth of God is meant the incomprehensibility of His essence; by length, the procession of His all-pervading power; by breadth, His overspreading all things, inasmuch as all things lie under His protection.
Reply to Objection 2: Man is said to be after the image of God, not as regards his body, but as regards that whereby he excels other animals. Hence, when it is said, "Let us make man to our image and likeness", it is added, "And let him have dominion over the fishes of the sea" (Gn. 1:26). Now man excels all animals by his reason and intelligence; hence it is according to his intelligence and reason, which are incorporeal, that man is said to be according to the image of God.
Reply to Objection 3: Corporeal parts are attributed to God in Scripture on account of His actions, and this is owing to a certain parallel. For instance the act of the eye is to see; hence the eye attributed to God signifies His power of seeing intellectually, not sensibly; and so on with the other parts.
Reply to Objection 4: Whatever pertains to posture, also, is only attributed to God by some sort of parallel. He is spoken of as sitting, on account of His unchangeableness and dominion; and as standing, on account of His power of overcoming whatever withstands Him.
Reply to Objection 5: We draw near to God by no corporeal steps, since He is everywhere, but by the affections of our soul, and by the actions of that same soul do we withdraw from Him; thus, to draw near to or to withdraw signifies merely spiritual actions based on the metaphor of local motion.
Objection 1: It seems that God is composed of matter and form. For whatever has a soul is composed of matter and form; since the soul is the form of the body. But Scripture attributes a soul to God; for it is mentioned in Hebrews (Heb. 10:38), where God says: "But My just man liveth by faith; but if he withdraw himself, he shall not please My soul." Therefore God is composed of matter and form.
Objection 2: Further, anger, joy and the like are passions of the composite. But these are attributed to God in Scripture: "The Lord was exceeding angry with His people" (Ps. 105:40). Therefore God is composed of matter and form.
Objection 3: Further, matter is the principle of individualization. But God seems to be individual, for He cannot be predicated of many. Therefore He is composed of matter and form.
On the contrary, Whatever is composed of matter and form is a body; for dimensive quantity is the first property of matter. But God is not a body as proved in the preceding Article; therefore He is not composed of matter and form.
I answer that, It is impossible that matter should exist in God. First, because matter is in potentiality. But we have shown (Q[2], A[3]) that God is pure act, without any potentiality. Hence it is impossible that God should be composed of matter and form. Secondly, because everything composed of matter and form owes its perfection and goodness to its form; therefore its goodness is participated, inasmuch as matter participates the form. Now the first good and the best---viz. God---is not a participated good, because the essential good is prior to the participated good. Hence it is impossible that God should be composed of matter and form. Thirdly, because every agent acts by its form; hence the manner in which it has its form is the manner in which it is an agent. Therefore whatever is primarily and essentially an agent must be primarily and essentially form. Now God is the first agent, since He is the first efficient cause. He is therefore of His essence a form; and not composed of matter and form.
Reply to Objection 1: A soul is attributed to God because His acts resemble the acts of a soul; for, that we will anything, is due to our soul. Hence what is pleasing to His will is said to be pleasing to His soul.
Reply to Objection 2: Anger and the like are attributed to God on account of a similitude of effect. Thus, because to punish is properly the act of an angry man, God's punishment is metaphorically spoken of as His anger.
Reply to Objection 3: Forms which can be received in matter are individualized by matter, which cannot be in another as in a subject since it is the first underlying subject; although form of itself, unless something else prevents it, can be received by many. But that form which cannot be received in matter, but is self-subsisting, is individualized precisely because it cannot be received in a subject; and such a form is God. Hence it does not follow that matter exists in God.
Objection 1: It seems that God is not the same as His essence or nature. For nothing can be in itself. But the substance or nature of God---i.e. the Godhead---is said to be in God. Therefore it seems that God is not the same as His essence or nature.
Objection 2: Further, the effect is assimilated to its cause; for every agent produces its like. But in created things the "suppositum" is not identical with its nature; for a man is not the same as his humanity. Therefore God is not the same as His Godhead.
On the contrary, It is said of God that He is life itself, and not only that He is a living thing: "I am the way, the truth, and the life" (Jn. 14:6). Now the relation between Godhead and God is the same as the relation between life and a living thing. Therefore God is His very Godhead.
I answer that, God is the same as His essence or nature. To understand this, it must be noted that in things composed of matter and form, the nature or essence must differ from the "suppositum," because the essence or nature connotes only what is included in the definition of the species; as, humanity connotes all that is included in the definition of man, for it is by this that man is man, and it is this that humanity signifies, that, namely, whereby man is man. Now individual matter, with all the individualizing accidents, is not included in the definition of the species. For this particular flesh, these bones, this blackness or whiteness, etc., are not included in the definition of a man. Therefore this flesh, these bones, and the accidental qualities distinguishing this particular matter, are not included in humanity; and yet they are included in the thing which is man. Hence the thing which is a man has something more in it than has humanity. Consequently humanity and a man are not wholly identical; but humanity is taken to mean the formal part of a man, because the principles whereby a thing is defined are regarded as the formal constituent in regard to the individualizing matter. On the other hand, in things not composed of matter and form, in which individualization is not due to individual matter---that is to say, to "this" matter---the very forms being individualized of themselves---it is necessary the forms themselves should be subsisting "supposita." Therefore "suppositum" and nature in them are identified. Since God then is not composed of matter and form, He must be His own Godhead, His own Life, and whatever else is thus predicated of Him.
Reply to Objection 1: We can speak of simple things only as though they were like the composite things from which we derive our knowledge. Therefore in speaking of God, we use concrete nouns to signify His subsistence, because with us only those things subsist which are composite; and we use abstract nouns to signify His simplicity. In saying therefore that Godhead, or life, or the like are in God, we indicate the composite way in which our intellect understands, but not that there is any composition in God.
Reply to Objection 2: The effects of God do not imitate Him perfectly, but only as far as they are able; and the imitation is here defective, precisely because what is simple and one, can only be represented by divers things; consequently, composition is accidental to them, and therefore, in them "suppositum" is not the same as nature.
Objection 1: It seems that essence and existence are not the same in God. For if it be so, then the divine being has nothing added to it. Now being to which no addition is made is universal being which is predicated of all things. Therefore it follows that God is being in general which can be predicated of everything. But this is false: "For men gave the incommunicable name to stones and wood" (Wis. 14:21). Therefore God's existence is not His essence.
Objection 2: Further, we can know "whether" God exists as said above (Q[2], A[2]); but we cannot know "what" He is. Therefore God's existence is not the same as His essence---that is, as His quiddity or nature.
On the contrary, Hilary says (Trin. vii): "In God existence is not an accidental quality, but subsisting truth." Therefore what subsists in God is His existence.
I answer that, God is not only His own essence, as shown in the preceding article, but also His own existence. This may be shown in several ways. First, whatever a thing has besides its essence must be caused either by the constituent principles of that essence (like a property that necessarily accompanies the species---as the faculty of laughing is proper to a man---and is caused by the constituent principles of the species), or by some exterior agent---as heat is caused in water by fire. Therefore, if the existence of a thing differs from its essence, this existence must be caused either by some exterior agent or by its essential principles. Now it is impossible for a thing's existence to be caused by its essential constituent principles, for nothing can be the sufficient cause of its own existence, if its existence is caused. Therefore that thing, whose existence differs from its essence, must have its existence caused by another. But this cannot be true of God; because we call God the first efficient cause. Therefore it is impossible that in God His existence should differ from His essence. Secondly, existence is that which makes every form or nature actual; for goodness and humanity are spoken of as actual, only because they are spoken of as existing. Therefore existence must be compared to essence, if the latter is a distinct reality, as actuality to potentiality. Therefore, since in God there is no potentiality, as shown above (A[1]), it follows that in Him essence does not differ from existence. Therefore His essence is His existence. Thirdly, because, just as that which has fire, but is not itself fire, is on fire by participation; so that which has existence but is not existence, is a being by participation. But God is His own essence, as shown above (A[3]) if, therefore, He is not His own existence He will be not essential, but participated being. He will not therefore be the first being---which is absurd. Therefore God is His own existence, and not merely His own essence.
Reply to Objection 1: A thing that has nothing added to it can be of two kinds. Either its essence precludes any addition; thus, for example, it is of the essence of an irrational animal to be without reason. Or we may understand a thing to have nothing added to it, inasmuch as its essence does not require that anything should be added to it; thus the genus animal is without reason, because it is not of the essence of animal in general to have reason; but neither is it to lack reason. And so the divine being has nothing added to it in the first sense; whereas universal being has nothing added to it in the second sense.
Reply to Objection 2: "To be" can mean either of two things. It may mean the act of essence, or it may mean the composition of a proposition effected by the mind in joining a predicate to a subject. Taking "to be" in the first sense, we cannot understand God's existence nor His essence; but only in the second sense. We know that this proposition which we form about God when we say "God is," is true; and this we know from His effects (Q[2], A[2]).
Objection 1: It seems that God is contained in a genus. For a substance is a being that subsists of itself. But this is especially true of God. Therefore God is in a genus of substance.
Objection 2: Further, nothing can be measured save by something of its own genus; as length is measured by length and numbers by number. But God is the measure of all substances, as the Commentator shows (Metaph. x). Therefore God is in the genus of substance.
On the contrary, In the mind, genus is prior to what it contains. But nothing is prior to God either really or mentally. Therefore God is not in any genus.
I answer that, A thing can be in a genus in two ways; either absolutely and properly, as a species contained under a genus; or as being reducible to it, as principles and privations. For example, a point and unity are reduced to the genus of quantity, as its principles; while blindness and all other privations are reduced to the genus of habit. But in neither way is God in a genus. That He cannot be a species of any genus may be shown in three ways. First, because a species is constituted of genus and difference. Now that from which the difference constituting the species is derived, is always related to that from which the genus is derived, as actuality is related to potentiality. For animal is derived from sensitive nature, by concretion as it were, for that is animal, which has a sensitive nature. Rational being, on the other hand, is derived from intellectual nature, because that is rational, which has an intellectual nature, and intelligence is compared to sense, as actuality is to potentiality. The same argument holds good in other things. Hence since in God actuality is not added to potentiality, it is impossible that He should be in any genus as a species. Secondly, since the existence of God is His essence, if God were in any genus, He would be the genus "being", because, since genus is predicated as an essential it refers to the essence of a thing. But the Philosopher has shown (Metaph. iii) that being cannot be a genus, for every genus has differences distinct from its generic essence. Now no difference can exist distinct from being; for non-being cannot be a difference. It follows then that God is not in a genus. Thirdly, because all in one genus agree in the quiddity or essence of the genus which is predicated of them as an essential, but they differ in their existence. For the existence of man and of horse is not the same; as also of this man and that man: thus in every member of a genus, existence and quiddity---i.e. essence---must differ. But in God they do not differ, as shown in the preceding article. Therefore it is plain that God is not in a genus as if He were a species. From this it is also plain that He has no genus nor difference, nor can there be any definition of Him; nor, save through His effects, a demonstration of Him: for a definition is from genus and difference; and the mean of a demonstration is a definition. That God is not in a genus, as reducible to it as its principle, is clear from this, that a principle reducible to any genus does not extend beyond that genus; as, a point is the principle of continuous quantity alone; and unity, of discontinuous quantity. But God is the principle of all being. Therefore He is not contained in any genus as its principle.
Reply to Objection 1: The word substance signifies not only what exists of itself---for existence cannot of itself be a genus, as shown in the body of the article; but, it also signifies an essence that has the property of existing in this way---namely, of existing of itself; this existence, however, is not its essence. Thus it is clear that God is not in the genus of substance.
Reply to Objection 2: This objection turns upon proportionate measure which must be homogeneous with what is measured. Now, God is not a measure proportionate to anything. Still, He is called the measure of all things, in the sense that everything has being only according as it resembles Him.
Objection 1: It seems that there are accidents in God. For substance cannot be an accident, as Aristotle says (Phys. i). Therefore that which is an accident in one, cannot, in another, be a substance. Thus it is proved that heat cannot be the substantial form of fire, because it is an accident in other things. But wisdom, virtue, and the like, which are accidents in us, are attributes of God. Therefore in God there are accidents.
Objection 2: Further, in every genus there is a first principle. But there are many "genera" of accidents. If, therefore, the primal members of these genera are not in God, there will be many primal beings other than God---which is absurd.
On the contrary, Every accident is in a subject. But God cannot be a subject, for "no simple form can be a subject", as Boethius says (De Trin.). Therefore in God there cannot be any accident.
I answer that, From all we have said, it is clear there can be no accident in God. First, because a subject is compared to its accidents as potentiality to actuality; for a subject is in some sense made actual by its accidents. But there can be no potentiality in God, as was shown (Q[2], A[3]). Secondly, because God is His own existence; and as Boethius says (Hebdom.), although every essence may have something superadded to it, this cannot apply to absolute being: thus a heated substance can have something extraneous to heat added to it, as whiteness, nevertheless absolute heat can have nothing else than heat. Thirdly, because what is essential is prior to what is accidental. Whence as God is absolute primal being, there can be in Him nothing accidental. Neither can He have any essential accidents (as the capability of laughing is an essential accident of man), because such accidents are caused by the constituent principles of the subject. Now there can be nothing caused in God, since He is the first cause. Hence it follows that there is no accident in God.
Reply to Objection 1: Virtue and wisdom are not predicated of God and of us univocally. Hence it does not follow that there are accidents in God as there are in us.
Reply to Objection 2: Since substance is prior to its accidents, the principles of accidents are reducible to the principles of the substance as to that which is prior; although God is not first as if contained in the genus of substance; yet He is first in respect to all being, outside of every genus.
Objection 1: It seems that God is not altogether simple. For whatever is from God must imitate Him. Thus from the first being are all beings; and from the first good is all good. But in the things which God has made, nothing is altogether simple. Therefore neither is God altogether simple.
Objection 2: Further, whatever is best must be attributed to God. But with us that which is composite is better than that which is simple; thus, chemical compounds are better than simple elements, and animals than the parts that compose them. Therefore it cannot be said that God is altogether simple.
On the contrary, Augustine says (De Trin. iv, 6,7): "God is truly and absolutely simple."
I answer that, The absolute simplicity of God may be shown in many ways. First, from the previous articles of this question. For there is neither composition of quantitative parts in God, since He is not a body; nor composition of matter and form; nor does His nature differ from His "suppositum"; nor His essence from His existence; neither is there in Him composition of genus and difference, nor of subject and accident. Therefore, it is clear that God is nowise composite, but is altogether simple. Secondly, because every composite is posterior to its component parts, and is dependent on them; but God is the first being, as shown above (Q[2], A[3]). Thirdly, because every composite has a cause, for things in themselves different cannot unite unless something causes them to unite. But God is uncaused, as shown above (Q[2], A[3]), since He is the first efficient cause. Fourthly, because in every composite there must be potentiality and actuality; but this does not apply to God; for either one of the parts actuates another, or at least all the parts are potential to the whole. Fifthly, because nothing composite can be predicated of any single one of its parts. And this is evident in a whole made up of dissimilar parts; for no part of a man is a man, nor any of the parts of the foot, a foot. But in wholes made up of similar parts, although something which is predicated of the whole may be predicated of a part (as a part of the air is air, and a part of water, water), nevertheless certain things are predicable of the whole which cannot be predicated of any of the parts; for instance, if the whole volume of water is two cubits, no part of it can be two cubits. Thus in every composite there is something which is not it itself. But, even if this could be said of whatever has a form, viz. that it has something which is not it itself, as in a white object there is something which does not belong to the essence of white; nevertheless in the form itself, there is nothing besides itself. And so, since God is absolute form, or rather absolute being, He can be in no way composite. Hilary implies this argument, when he says (De Trin. vii): "God, Who is strength, is not made up of things that are weak; nor is He Who is light, composed of things that are dim."
Reply to Objection 1: Whatever is from God imitates Him, as caused things imitate the first cause. But it is of the essence of a thing to be in some sort composite; because at least its existence differs from its essence, as will be shown hereafter, (Q[4], A[3]).
Reply to Objection 2: With us composite things are better than simple things, because the perfections of created goodness cannot be found in one simple thing, but in many things. But the perfection of divine goodness is found in one simple thing (Q[4], A[1] and Q[6], A[2]).
Objection 1: It seems that God enters into the composition of other things, for Dionysius says (Coel. Hier. iv): "The being of all things is that which is above being---the Godhead." But the being of all things enters into the composition of everything. Therefore God enters into the composition of other things.
Objection 2: Further, God is a form; for Augustine says (De Verb. Dom., [*Serm. xxxviii]) that, "the word of God, which is God, is an uncreated form." But a form is part of a compound. Therefore God is part of some compound.
Objection 3: Further, whatever things exist, in no way differing from each other, are the same. But God and primary matter exist, and in no way differ from each other. Therefore they are absolutely the same. But primary matter enters into the composition things. Therefore also does God. Proof of the minor---whatever things differ, they differ by some differences, and therefore must be composite. But God and primary matter are altogether simple. Therefore they nowise differ from each other.
On the contrary, Dionysius says (Div. Nom. ii): "There can be no touching Him," i.e. God, "nor any other union with Him by mingling part with part."
Further, the first cause rules all things without commingling with them, as the Philosopher says (De Causis).
I answer that, On this point there have been three errors. Some have affirmed that God is the world-soul, as is clear from Augustine (De Civ. Dei vii, 6). This is practically the same as the opinion of those who assert that God is the soul of the highest heaven. Again, others have said that God is the formal principle of all things; and this was the theory of the Almaricians. The third error is that of David of Dinant, who most absurdly taught that God was primary matter. Now all these contain manifest untruth; since it is not possible for God to enter into the composition of anything, either as a formal or a material principle. First, because God is the first efficient cause. Now the efficient cause is not identical numerically with the form of the thing caused, but only specifically: for man begets man. But primary matter can be neither numerically nor specifically identical with an efficient cause; for the former is merely potential, while the latter is actual. Secondly, because, since God is the first efficient cause, to act belongs to Him primarily and essentially. But that which enters into composition with anything does not act primarily and essentially, but rather the composite so acts; for the hand does not act, but the man by his hand; and, fire warms by its heat. Hence God cannot be part of a compound. Thirdly, because no part of a compound can be absolutely primal among beings---not even matter, nor form, though they are the primal parts of every compound. For matter is merely potential; and potentiality is absolutely posterior to actuality, as is clear from the foregoing (Q[3], A[1]): while a form which is part of a compound is a participated form; and as that which participates is posterior to that which is essential, so likewise is that which is participated; as fire in ignited objects is posterior to fire that is essentially such. Now it has been proved that God is absolutely primal being (Q[2], A[3]).
Reply to Objection 1: The Godhead is called the being of all things, as their efficient and exemplar cause, but not as being their essence.
Reply to Objection 2: The Word is an exemplar form; but not a form that is part of a compound.
Reply to Objection 3: Simple things do not differ by added differences---for this is the property of compounds. Thus man and horse differ by their differences, rational and irrational; which differences, however, do not differ from each other by other differences. Hence, to be quite accurate, it is better to say that they are, not different, but diverse. Hence, according to the Philosopher (Metaph. x), "things which are diverse are absolutely distinct, but things which are different differ by something." Therefore, strictly speaking, primary matter and God do not differ, but are by their very being, diverse. Hence it does not follow they are the same.