Our natural knowledge begins from sense. It can therefore extend so far as it can be led by sensible things. But our intellect cannot in this way attain insight into the divine essence. Sensible things are indeed effects of God, but they are not proportionate to the power of their cause, and for this reason the whole power of God cannot be known from them. Neither, consequently, can his essence be seen. But since effects depend on their cause, sensible things can lead us to know that God exists, and to know what is bound to be attributable to him as the first cause of all things, and as transcending all his effects. In this way we know that God is related to creatures as the cause of them all; that he differs from creatures, since he is none of the things caused by him; and that creatures are separated from God because God transcends them, not because of any defect in God. Q.13, Art.1. (Whether any name is applicable to God.)

According to the philosopher (I De Interpretatione, cap. i), words are the signs of concepts, and concepts are copies of things. It is thus plain that words refer to things through the medium of concepts. We can therefore name things in so far as we can understand them. Now it was proved in Q.12, Art.2, that in this life we cannot see God in his essence. But we do know God through creatures, as their principle, in terms of the excelling and the remote. We can accordingly apply to God names which are derived from creatures. Such a name, however, does not express what the divine essence is in itself, as "man" by its own meaning expresses the very essence of a man. The name "man" signifies the definition which explains the essence of a man, since it stands for the definition.

Q.13, Art.5. (Whether the things which are affirmed of God and also of creatures are affirmed of them univocally.)

It is impossible for anything to be predicated of God and of creatures univocally, because an effect which is not proportionate to the power of its active cause resembles its cause in an inadequate way. It does not have the same nature. What is separated and multiple in the effects is simple in the cause, in which it exists in a single mode. The sun, for example, produces many and various forms in inferior things, yet its power by which it does so is one. Similarly, the many perfections which exist separately in created things all pre-exist as a simple unity in God. Thus any name given to a perfection of a creature indicates a perfection which is distinct from its other perfections. When we call a man wise, for example, we name a perfection which is distinct from his essence as a man, and distinct from his power and from his existence. But when we apply this same name to God, we do not mean to signify anything distinct from his essence, power, or existence. Accordingly, when the name "wise" is applied to a man, it circumscribes and comprehends what it signifies. But when it is applied to God, it leaves what it signifies uncomprehended, and beyond its power to denote. It is thus plain that the name "wise" is not applied to God and to a man with the same meaning. This is true of other names also. No name is applied univocally to God and to creatures.

Yet neither are such names ascribed merely equivocally, as some have said. If they were, nothing could be known or proved of God at all. We should always fall into the fallacy of equivocation. But this is contrary to what the philosopher says in 8 Physics and in 12 Metaph., where he demonstrates many things about God. It is contrary also to Rom.1:20: "the invisible things of him are clearly seen, being understood by the things that are made." We must therefore say that it is by way of analogy, that is, according to a relation of proportion, that such names are ascribed to God as well as to creatures. There are two ways of applying a name analogously. First, when many things are related to one thing. Thus "healthy" is applied both to medicine and to urine, because these both relate to the health of an animal, one being the sign of it and the other the cause of it. Secondly, when the one thing is related to the other. Thus "healthy" is applied both to medicine and to an animal, because medicine is the cause of health in an animal. Now it is in this second analogous way that some names are ascribed both to God and to creatures, and such names are neither purely equivocal nor purely univocal. As we said in Art.1., it is only from what we know of creatures that we can ascribe names to God. But when we ascribe any one name to God as well as to creatures, we do so in accordance with the relation in which creatures stand to God as their principle and cause, in whom the perfection of all things pre-exist in an eminent way. This common ascription is midway between merely equivocal and purely univocal ascription. There is no one nature common to what is ascribed, as there is when things are ascribed univocally. Yet neither are the things ascribed entirely different, as they are when ascribed equivocally. A name ascribed in different senses by analogy signifies different relations to one and the same thing, as "healthy" signifies the sign of an animal's health when ascribed to urine, and the cause of its health when ascribed to medicine.