Summa Th. I EN Qu.2
Because the chief aim of sacred doctrine is to teach the knowledge of God, not only as He is in Himself, but also as He is the beginning of things and their last end, and especially of rational creatures, as is clear from what has been already said, therefore, in our endeavor to expound this science, we shall treat: (1) Of God; (2) Of the rational creature's advance towards God; (3) Of Christ, Who as man, is our way to God.
In treating of God there will be a threefold division, for we shall consider: (1) Whatever concerns the Divine Essence; (2) Whatever concerns the distinctions of Persons; (3) Whatever concerns the procession of creatures from Him.
Concerning the Divine Essence, we must consider: (1) Whether God exists? (2) The manner of His existence, or, rather, what is NOT the manner of His existence; (3) Whatever concerns His operations---namely, His knowledge, will, power.
Concerning the first, there are three points of inquiry:
(1) Whether the proposition "God exists" is self-evident?
(2) Whether it is demonstrable?
(3) Whether God exists?
Objection: 1. It seems that the existence of God is self-evident. Now those things are said to be self-evident to us the knowledge of which is naturally implanted in us, as we can see in regard to first principles. But as Damascene says (De Fide Orth. i, 1,3), "the knowledge of God is naturally implanted in all." Therefore the existence of God is self-evident.
2. Further, those things are said to be self-evident which are known as soon as the terms are known, which the Philosopher (1 Poster. iii) says is true of the first principles of demonstration. Thus, when the nature of a whole and of a part is known, it is at once recognized that every whole is greater than its part. But as soon as the signification of the word "God" is understood, it is at once seen that God exists. For by this word is signified that thing than which nothing greater can be conceived. But that which exists actually and mentally is greater than that which exists only mentally. Therefore, since as soon as the word "God" is understood it exists mentally, it also follows that it exists actually. Therefore the proposition "God exists" is self-evident.
3. Further, the existence of truth is self-evident. For whoever denies the existence of truth grants that truth does not exist: and, if truth does not exist, then the proposition "Truth does not exist" is true: and if there is anything true, there must be truth. But God is truth itself: "I am the way, the truth, and the life" (Jn 14,6) Therefore "God exists" is self-evident.
On the contrary No one can mentally admit the opposite of what is self-evident; as the Philosopher (Metaph. iv, lect. vi) states concerning the first principles of demonstration. But the opposite of the proposition "God is" can be mentally admitted: "The fool said in his heart, There is no God" (Ps 52,1). Therefore, that God exists is not self-evident.
I answer that A thing can be self-evident in either of two ways: on the one hand, self-evident in itself, though not to us; on the other, self-evident in itself, and to us. A proposition is self-evident because the predicate is included in the essence of the subject, as "Man is an animal," for animal is contained in the essence of man. If, therefore the essence of the predicate and subject be known to all, the proposition will be self-evident to all; as is clear with regard to the first principles of demonstration, the terms of which are common things that no one is ignorant of, such as being and non-being, whole and part, and such like. If, however, there are some to whom the essence of the predicate and subject is unknown, the proposition will be self-evident in itself, but not to those who do not know the meaning of the predicate and subject of the proposition. Therefore, it happens, as Boethius says (Hebdom., the title of which is: "Whether all that is, is good"), "that there are some mental concepts self-evident only to the learned, as that incorporeal substances are not in space." Therefore I say that this proposition, "God exists," of itself is self-evident, for the predicate is the same as the subject, because God is His own existence as will be hereafter shown (Question , Article ). Now because we do not know the essence of God, the proposition is not self-evident to us; but needs to be demonstrated by things that are more known to us, though less known in their nature---namely, by effects.
Reply to Objection: 1. To know that God exists in a general and confused way is implanted in us by nature, inasmuch as God is man's beatitude. For man naturally desires happiness, and what is naturally desired by man must be naturally known to him. This, however, is not to know absolutely that God exists; just as to know that someone is approaching is not the same as to know that Peter is approaching, even though it is Peter who is approaching; for many there are who imagine that man's perfect good which is happiness, consists in riches, and others in pleasures, and others in something else.
2. Perhaps not everyone who hears this word "God" understands it to signify something than which nothing greater can be thought, seeing that some have believed God to be a body. Yet, granted that everyone understands that by this word "God" is signified something than which nothing greater can be thought, nevertheless, it does not therefore follow that he understands that what the word signifies exists actually, but only that it exists mentally. Nor can it be argued that it actually exists, unless it be admitted that there actually exists something than which nothing greater can be thought; and this precisely is not admitted by those who hold that God does not exist.
3. The existence of truth in general is self-evident but the existence of a Primal Truth is not self-evident to us.
Objection: 1. It seems that the existence of God cannot be demonstrated. For it is an article of faith that God exists. But what is of faith cannot be demonstrated, because a demonstration produces scientific knowledge; whereas faith is of the unseen (He 11,1). Therefore it cannot be demonstrated that God exists.
2. Further, the essence is the middle term of demonstration. But we cannot know in what God's essence consists, but solely in what it does not consist; as Damascene says (De Fide Orth. i, 4). Therefore we cannot demonstrate that God exists.
3. Further, if the existence of God were demonstrated, this could only be from His effects. But His effects are not proportionate to Him, since He is infinite and His effects are finite; and between the finite and infinite there is no proportion. Therefore, since a cause cannot be demonstrated by an effect not proportionate to it, it seems that the existence of God cannot be demonstrated.
On the contrary The Apostle says: "The invisible things of Him are clearly seen, being understood by the things that are made" (Rm 1,20). But this would not be unless the existence of God could be demonstrated through the things that are made; for the first thing we must know of anything is whether it exists.
I answer that Demonstration can be made in two ways: One is through the cause, and is called "a priori," and this is to argue from what is prior absolutely. The other is through the effect, and is called a demonstration "a posteriori"; this is to argue from what is prior relatively only to us. When an effect is better known to us than its cause, from the effect we proceed to the knowledge of the cause. And from every effect the existence of its proper cause can be demonstrated, so long as its effects are better known to us; because since every effect depends upon its cause, if the effect exists, the cause must pre-exist. Hence the existence of God, in so far as it is not self-evident to us, can be demonstrated from those of His effects which are known to us.
Reply to Objection: 1. The existence of God and other like truths about God, which can be known by natural reason, are not articles of faith, but are preambles to the articles; for faith presupposes natural knowledge, even as grace presupposes nature, and perfection supposes something that can be perfected. Nevertheless, there is nothing to prevent a man, who cannot grasp a proof, accepting, as a matter of faith, something which in itself is capable of being scientifically known and demonstrated.
2. When the existence of a cause is demonstrated from an effect, this effect takes the place of the definition of the cause in proof of the cause's existence. This is especially the case in regard to God, because, in order to prove the existence of anything, it is necessary to accept as a middle term the meaning of the word, and not its essence, for the question of its essence follows on the question of its existence. Now the names given to God are derived from His effects; consequently, in demonstrating the existence of God from His effects, we may take for the middle term the meaning of the word "God".
3. From effects not proportionate to the cause no perfect knowledge of that cause can be obtained. Yet from every effect the existence of the cause can be clearly demonstrated, and so we can demonstrate the existence of God from His effects; though from them we cannot perfectly know God as He is in His essence.
Objection: 1. It seems that God does not exist; because if one of two contraries be infinite, the other would be altogether destroyed. But the word "God" means that He is infinite goodness. If, therefore, God existed, there would be no evil discoverable; but there is evil in the world. Therefore God does not exist.
2. Further, it is superfluous to suppose that what can be accounted for by a few principles has been produced by many. But it seems that everything we see in the world can be accounted for by other principles, supposing God did not exist. For all natural things can be reduced to one principle which is nature; and all voluntary things can be reduced to one principle which is human reason, or will. Therefore there is no need to suppose God's existence.
On the contrary It is said in the person of God: "I am Who am." (Ex 3,14)
I answer that The existence of God can be proved in five ways. in, and evident to our senses, that in the world some things are in motion. Now whatever is in motion is put in motion by another, for nothing can be in motion except it is in potentiality to that towards which it is in motion; whereas a thing moves inasmuch as it is in act. For motion is nothing else than the reduction of something from potentiality to actuality. But nothing can be reduced from potentiality to actuality, except by something in a state of actuality. Thus that which is actually hot, as fire, makes wood, which is potentially hot, to be actually hot, and thereby moves and changes it. Now it is not possible that the same thing should be at once in actuality and potentiality in the same respect, but only in different respects. For what is actually hot cannot simultaneously be potentially hot; but it is simultaneously potentially cold. It is therefore impossible that in the same respect and in the same way a thing should be both mover and moved, i.e. that it should move itself. Therefore, whatever is in motion must be put in motion by another. If that by which it is put in motion be itself put in motion, then this also must needs be put in motion by another, and that by another again. But this cannot go on to infinity, because then there would be no first mover, and, consequently, no other mover; seeing that subsequent movers move only inasmuch as they are put in motion by the first mover; as the staff moves only because it is put in motion by the hand. Therefore it is necessary to arrive at a first mover, put in motion by no other; and this everyone understands to be God.
rom the nature of the efficient cause. In the world of sense we find there is an order of efficient causes. There is no case known (neither is it, indeed, possible) in which a thing is found to be the efficient cause of itself; for so it would be prior to itself, which is impossible. Now in efficient causes it is not possible to go on to infinity, because in all efficient causes following in order, the first is the cause of the intermediate cause, and the intermediate is the cause of the ultimate cause, whether the intermediate cause be several, or only one. Now to take away the cause is to take away the effect. Therefore, if there be no first cause among efficient causes, there will be no ultimate, nor any intermediate cause. But if in efficient causes it is possible to go on to infinity, there will be no first efficient cause, neither will there be an ultimate effect, nor any intermediate efficient causes; all of which is plainly false. Therefore it is necessary to admit a first efficient cause, to which everyone gives the name of God.
ken from possibility and necessity, and runs thus. We find in nature things that are possible to be and not to be, since they are found to be generated, and to corrupt, and consequently, they are possible to be and not to be. But it is impossible for these always to exist, for that which is possible not to be at some time is not. Therefore, if everything is possible not to be, then at one time there could have been nothing in existence. Now if this were true, even now there would be nothing in existence, because that which does not exist only begins to exist by something already existing. Therefore, if at one time nothing was in existence, it would have been impossible for anything to have begun to exist; and thus even now nothing would be in existence---which is absurd. Therefore, not all beings are merely possible, but there must exist something the existence of which is necessary. But every necessary thing either has its necessity caused by another, or not. Now it is impossible to go on to infinity in necessary things which have their necessity caused by another, as has been already proved in regard to efficient causes. Therefore we cannot but postulate the existence of some being having of itself its own necessity, and not receiving it from another, but rather causing in others their necessity. This all men speak of as God.
aken from the gradation to be found in things. Among beings there are some more and some less good, true, noble and the like. But "more" and "less" are predicated of different things, according as they resemble in their different ways something which is the maximum, as a thing is said to be hotter according as it more nearly resembles that which is hottest; so that there is something which is truest, something best, something noblest and, consequently, something which is uttermost being; for those things that are greatest in truth are greatest in being, as it is written in Metaph. ii. Now the maximum in any genus is the cause of all in that genus; as fire, which is the maximum heat, is the cause of all hot things. Therefore there must also be something which is to all beings the cause of their being, goodness, and every other perfection; and this we call God.
ken from the governance of the world. We see that things which lack intelligence, such as natural bodies, act for an end, and this is evident from their acting always, or nearly always, in the same way, so as to obtain the best result. Hence it is plain that not fortuitously, but designedly, do they achieve their end. Now whatever lacks intelligence cannot move towards an end, unless it be directed by some being endowed with knowledge and intelligence; as the arrow is shot to its mark by the archer. Therefore some intelligent being exists by whom all natural things are directed to their end; and this being we call God.
Reply to Objection: 1. As Augustine says (Enchiridion xi): "Since God is the highest good, He would not allow any evil to exist in His works, unless His omnipotence and goodness were such as to bring good even out of evil." This is part of the infinite goodness of God, that He should allow evil to exist, and out of it produce good.
2. Since nature works for a determinate end under the direction of a higher agent, whatever is done by nature must needs be traced back to God, as to its first cause. So also whatever is done voluntarily must also be traced back to some higher cause other than human reason or will, since these can change or fail; for all things that are changeable and capable of defect must be traced back to an immovable and self-necessary first principle, as was shown in the body of the Article.
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" (Jb 11,8-9). Therefore God is a body.
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" (He 1,3). Therefore God is a body.
3. Further, whatever has corporeal parts is a body. Now Scripture attributes corporeal parts to God. "Hast thou an arm like God?" (Jb 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.
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.
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" (Jr 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.
1. First, because no body is in motion unless it be put in motion, as is evident from induction. Now it has been already proved (Question , Article ), that God is the First Mover, and is Himself unmoved. Therefore it is clear that God is not a body.
2. 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.
3. 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 (Question , Article ), 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.
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.
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.
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.
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 (He 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.
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.
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.
1. First, because matter is in potentiality. But we have shown (Question , Article ) that God is pure act, without any potentiality. Hence it is impossible that God should be composed of matter and form.
2. 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.
3. 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.
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.
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.
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.
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" (Sg 14,21). Therefore God's existence is not His essence.
2. Further, we can know "whether" God exists as said above (Question , Article ); 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.
1. 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.
2. 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 (Article ), it follows that in Him essence does not differ from existence. Therefore His essence is His existence.
3.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 (Article ) 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.
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 (Question , Article ).
Summa Th. I EN Qu.2