Chapter 10 — Of the opinion of those who say it cannot be demonstrated that there is a God, since this is self-evident

It may seem useless to some to endeavor to show that there is a God: they say that it is self-evident that God is, so that it is impossible to think the contrary, and thus it cannot be demonstrated that there is a God. The reasons for this view are as follow.

Those things are said to be self-evident which are known as soon as the terms are known; thus, as soon as it is known what is a whole, and what is a part, it is known that the whole is greater than its part. Now such is the statement “God is.” For by this word “God” we understand a thing than which a greater cannot be thought of. This is what a man conceives in his mind when he hears and understands this word “God”: so that God must already be at least in his mind. Nor can he be in the mind alone, for that which is both in the mind and in reality is greater than that which is in the mind only. And the very signification of the word shows that nothing is greater than God. Therefore, it follows that God’s existence is self-evident, since it is made clear from the very signification of the word.

Again. It is possible to think that there is a thing which cannot be thought not to exist, and such a thing is evidently greater than that which can be thought not to exist. Therefore, if God can be thought not to exist, it follows that something can be thought greater than God, and this is contrary to the signification of the term. Therefore, it remains that God’s existence is self-evident.

Further. Those propositions are most evident in which the selfsame thing is predicated of itself, such as: “man is man”; or in which the predicate is included in the definition of the subject, for instance: “man is an animal.” Now, as we shall show further on, (Ch. 22.) in God alone do we find that his being is his essence: so that the answer is the same to the question, “What is he?” as to the question, “Is he?” Accordingly, when we say, “God is,” the predicate is either identified with the subject, or at least is included in the definition of the subject. And thus it will be self-evident that God is.

Moreover. Things that are known naturally are self-evident, for it is not by a process of research that they become evident. Now it is naturally known that God is, since man’s desire tends naturally to God as his last end, as we shall show further on. (Bk. 3, ch. 25.) Therefore, it is self-evident that God is.

Again. That by which all things are known must be self-evident. Now God is such. For just as the light of the sun is the principle of all visual perception, so the divine light is the principle of all intellectual knowledge, because it is in it that the first and greatest intellectual light is found. Therefore, it must be self-evident that God is.

On account of these and similar arguments some are of the opinion that God’s existence is so self-evident that the mind cannot think the contrary.