Summa Theologica, Part I (Prima Pars) From the Complete...

Reply Obj. 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.

Obj. 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" (John 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.

Reply Obj. 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 Obj. 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.

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 Obj. 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 Obj. 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). ______________________

Obj. 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.

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 Obj. 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 Obj. 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.

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 Obj. 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.

Obj. 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.