My purpose (he says) is to declare the truth which the Catholic Faith professes. But here I must have recourse to natural reason, since the gentiles do not accept the authority of Scripture. Natural reason, however, is deficient in the things of God; it can prove some parts of the faith, but not others. It can prove the existence of God and the immortality of the soul, but not the Trinity, the Incarnation, or the Last Judgement. Whatever is demonstrable is, so far as it goes, in accordance with the Christian faith, and nothing in revelation is contrary to reason. But it is important to separate the parts of the faith which can be proved by reason from those which cannot. Accordingly, of the four books into which the Summa is divided, the first three make no appeal to revelation, except to show that it is in accordance with conclusions reached by reason; only in the fourth book are matters treated which cannot be known apart from revelation.
The first step is to prove the existence of God. Some think this unnecessary, since the existence of God (they say) is self-evident. If we knew God’s essence, this would be true, since (as is proved later) in God, essence and existence are one. But we do not know His essence, except very imperfectly. Wise men know more of his essence than do the ignorant, and angels know more than either; but no creature knows enough of it to be able to deduce God’s existence from His essence. On this ground, the ontological argument is rejected.
It is important to remember that religious truth which can be proved can also be known by faith. The proofs are difficult, and can only be understood by the learned; but faith is necessary also to the ignorant, to the young, and to those who, from practical preoccupations, have not the leisure to learn philosophy. For them, revelation suffices.
Some say that God is only knowable by faith. They argue that, if
-454-
the principles of demonstration became known to us through experience derived from the senses, as is said in the Posterior Analytics, whatever transcends sense cannot be proved. This, however, is false; and even if it were true, God could be known from His sensible effects.
The existence of God is proved, as in Aristotle, by the argument of the unmoved mover. * There are things which are only moved, and other things which both move and are moved. Whatever is moved is moved by something, and, since an endless regress is impossible, we must arrive somewhere at something which moves without being moved. This unmoved mover is God. It might be objected that this argument involves the eternity of movement, which Catholics reject. This would be an error: it is valid on the hypothesis of the eternity of movement, but is only strengthened by the opposite hypothesis, which involves a beginning, and therefore a First Cause.
In the Summa Theologiae, five proofs of God’s existence are given. First, the argument of the unmoved mover, as above. Second, the argument of the. First Cause, which again depends upon the impossibility of an infinite regress. Third, that there must be an ultimate source of all necessity; this is much the same as the second argument. Fourth, that we find various perfections in the world, and that these must have their source in something completely perfect. Fifth, that we find even lifeless things serving a purpose, which must be that of some being outside them, since only living things can have an internal purpose.
To return to the Summa contra Gentiles, having proved the existence of God, we can now say many things about Him, but these are all, in a sense, negative: God’s nature is only known to us through what it is not. God is eternal, since He is unmoved; He is unchanging, since He contains no passive potentiality. David of Dinant (a materialistic pantheist of the early thirteenth century) “raved” that God is the same as primary matter; this is absurd, since primary matter is pure passivity, and God is pure activity. In God, there is no composition, therefore He is not a body, because bodies have parts.
God is His own essence since otherwise He would not be simple, but would be compounded of essence and existence. (This point is
____________________
* But in Aristotle the argument leads to 47 or 55 Gods.
-455-
important.) In God, essence and existence are identical. There are no accidents in God. He cannot be specified by any substantial difference; He is not in any genus; He cannot be defined. But He lacks not the excellence of any genus. Things are in some ways like God, in others not. It is more fitting to say that things are like God than that God is like things.
God is good, and is His own goodness; He is the good of every good. He is intelligent, and His act of intelligence is His essence. He understands by His essence, and understands Himself perfectly. (John the Scot, it will be remembered, thought otherwise.)
Although there is no composition in the divine intellect, God understands many things. This might seem a difficulty, but the things that He understands have no distinct being in Him. Nor do they exist per se, as Plato thought, because forms of natural things cannot exist or be understood apart from matter. Nevertheless, God must understand forms before creating. The solution of this difficulty is as follows: “The concept of the divine intellect, according as He understands Himself, which concept is His Word, is the likeness not only of God Himself understood, but also of all the things of which the divine essence is the likeness. Accordingly many things can be understood by God, by one intelligible species which is the divine essence, and by one understood intention which is the divine Word.” * Every form, so far as it is something positive, is a perfection. God’s intellect includes in His essence what is proper to each thing, by understanding where it is like Him and where unlike; for instance life, not knowledge, is the essence of a plant, and knowledge, not intellect, is the essence of an animal. Thus a plant is like God in being alive, but unlike in not having knowledge; an animal is like God in having knowledge, but unlike in not having intellect. It is always by a negation that a creature differs from God.
God understands all things at the same instant. His knowledge is not a habit, and is not discursive or argumentative. God is truth. (This is to be understood literally.)
We come now to a question which had already troubled both Plato and Aristotle. Can God know particular things, or does He only know universals and general truths? A Christian, since he believes in Provi-
____________________
* Summa contra Gentiles, Bk. I, Ch. LIII.
-456-
dence, must hold that God knows particular things; nevertheless there are weighty arguments against this view. Saint Thomas enumerates seven such arguments, and then proceeds to refute them. The seven arguments are as follows:
Singularity being signate matter, nothing immaterial can know it.
Singulars do not always exist, and cannot be known when they do not exist; therefore they cannot be known by an unchanging being.
Singulars are contingent, not necessary; therefore there can be no certain knowledge of them except when they exist.
Some singulars are due to volitions, which can only be known to the person willing.
Singulars are infinite in number, and the infinite as such is unknown.
Singulars are too petty for God’s attention.
In some singulars there is evil, but God cannot know evil.
Aquinas replies that God knows singulars as their cause; that He knows things that do not yet exist, just as an artificer does when he is making something; that He knows future contingents, because He sees each thing in time as if present, He Himself being not in time; that He knows our minds and secret wills, and that He knows an infinity of things, although we cannot do so. He knows trivial things, because nothing is wholly trivial, and everything has some nobility; otherwise God would know only Himself. Moreover the order of the universe is very noble, and this cannot be known without knowing even the trivial parts. Finally, God knows evil things, because knowing anything good involves knowing the opposite evil.
In God there is Will; His Will is His essence, and its principal object is the divine essence. In willing Himself, God wills other things also, for God is the end of all things. He wills even things that are not yet. He wills His own being and goodness, but other things, though He wills them, He does not will necessarily. There is free will in God; a reason can be assigned for His volition, but not a cause. He cannot will things impossible in themselves; for example, He cannot make a contradiction true. The Saint’s example of something beyond even divine power is not an altogether happy one; he says that God could not make a man be an ass.
In God are delight and joy and love; God hates nothing, and pos-
-457-
sesses the contemplative and active virtues. He is happy, and is His own happiness.
We come
