to us, though less known in their nature namely, by effects. Reply Obj. 1. To know that God exists in a general and confused way is implanted in us by nature, inasmuch as God is man's beati- tude. 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 approach- ing, even though it is Peter who is approach- ing; for many there are who imagine that man's perfect good which is happiness, con- sists in riches, and others in pleasures, and others in something else. Reply Obj. 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 un- derstands that by this word "God" is signified something than which nothing greater can be thought, nevertheless, it does not therefore fol- low that he understands that what the word signifies exists actually, but only that it exists mentally. Nor can it be argued that it actu- ally 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. Reply Obj. 3. The existence of truth in gen- eral is self-evident but the existence of a Pri- mal Truth is not self-evident to us. ✓ SECOND ARTICLE Whether It Can Be Demonstrated That God Exists? We proceed thus to the Second Article:- 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 (Heb. xi. 1). Therefore it cannot be demonstrated that God exists. Obj. 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 Fid. Orth. i. 4). Therefore we cannot de- monstrate that God exists. Obj. 3. Further, if the existence of God were demonstrated, this could only be from His effects. But His effects are not propor- tionate 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 in- visible things of Him are clearly seen, being understood by the things that are made (Rom. i. 20). But this would not be unless the ex- istence 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 pos- teriori; 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 ef- fects 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 Obj. 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 sup- poses something that can be perfected. Never- theless, 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 demon- strated. Reply Obj. 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 espe- cially 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 ques- tion of its existence. Now the names given to God are derived from His effects; conse- quently, in demonstrating the existence of God from His effects, we may take for the middle term the meaning of the word "God." Reply Obj. 3. From effects not proportion- ate to the cause no perfect knowledge of that cause can be obtained. Yet from every effect the existence of the cause can be clearly dem- onstrated, and so we can demonstrate the ex- istence of God from His effects; though from them we cannot perfectly know God as He is in His essence. The Existence of God (In Three Articles) 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 con- cerns 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? FIRST ARTICLE Whether the Existence of God Is Self-Evident? We proceed thus to the First Article:- 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 Dam- ascene says (De Fid. Orth. i. 1, 3), the knowledge of God is naturally implanted in all. Therefore the existence of God is self- evident. Obj. 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 princi- ples 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 11 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. Obj. 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 (John xiv. 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 con- cerning 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. lii. 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 predi cate 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 com- mon 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 un- known, 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 Boëthi- us 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 proposi- tion, "God exists," of itself is self-evident, for the predicate is the same as the subject; be- cause God is His own existence as will be here- after shown (Q. 3, A. 4). Now because we do not know the essence of God, the proposi- tion is not self-evident to us; but needs to be demonstrated by things that are more known

Read the preamble to ST I.2.1 (Summa Theologiae, Part I, Question 2, article 1). What is
the chief aim of this science? Be sure to cite the text.