Book Four — Salvation, Chapter 11 — Summa Contra Gentiles
[1] As starting point for this intention, one must take this: Following a diversity of natures, one finds a diverse manner of emanation in things, and, the higher a nature is, the more intimate to the nature is that which flows from it.
[2] For, in all things, inanimate bodies have the lowest place. There can be no emanations in these except by the action of some one upon another one. For this is the way in which fire is generated by fire, when an extraneous body is changed by the fire and is brought to the quality and species of fire.
[3] Among animate bodies the next place is held by the plants, and in these the emanation does proceed somewhat from what is within: to the extent, namely, that the internal humor of the plant is converted into seed and that the seed committed to the soil grows into a plant. Here, then, one has already found the first grade of life, for living things are those which move themselves to action, but those which can move only things external to them are entirely devoid of life. And in plants this is the mark of life: that which is within, them moves toward some form. The life of plants is nevertheless imperfect; this is because, although the emanation in plants proceeds from what is within, what comes forth little by little in the emanation is, at the end, found to be entirely external. For the humor first emerging from the tree becomes a blossom, and at length a fruit distinct from the tree’s bark, yet still fastened to it. But, when the fruit is perfected, it is separated from the tree altogether; it falls to the ground and its seeding power produces another plant. If one also considers this carefully, he will see that originally this emanation comes from what is external, for the internal humor of the tree is taken through the roots from the soil from which the plant receives nourishment.
[4] Beyond the life of plants one finds a higher grade of life: that of the sensitive soul. Its emanation may have an external beginning, but has an internal termination, and, the more fully the emanation proceeds, the more it reaches what is within. For the exterior sensible impresses its form on the exterior senses; from these it proceeds to the imagination and, further, to the storehouse of the memory. Nevertheless, in each step of this emanation the principle and the term refer to different things; no sensitive power reflects upon itself. This grade of life, then, is higher than the life of plants—higher to the extent that its operation takes place within the principles which are within; it is, nevertheless, not an entirely perfect life, since the emanation is always from some first to some second.
[5] That, then, is the supreme and perfect grade of life which is in the intellect, for the intellect reflects upon itself and the intellect can understand itself. But even in the intellectual life one finds diverse grades. For the human intellect, although it can know itself, does indeed take the first beginning of its knowledge from without, because it cannot understand without a phantasm, as is clear from the things said before. There is, therefore, a more perfect intellectual life in the angels. In them the intellect does not proceed to self-knowledge from anything exterior, but knows itself through itself. Nonetheless, it is not the ultimate perfection to which their life belongs. The reason is this: Although the intention understood is entirely intrinsic to them, the very intention understood is not their substance, for in them understanding is not identified with being (as is clear from the foregoing). Therefore, the ultimate perfection of life belongs to God, in whom understanding is not other than being, as has been shown; accordingly, the intention understood in God must be the divine essence itself.
[6] Now, I mean by the “intention understood” what the intellect conceives in itself of the thing understood. To be sure, in us this is neither the thing which is understood nor is it the very substance of the intellect. But it is a certain likeness of the thing understood conceived in the intellect, and which the exterior words signify. So, the intention itself is named the “interior word” which is signified by the exterior word. Indeed, that the intention aforesaid is not within us the thing understood is clear from this: It is one thing to understand a thing, and another to understand the intention itself, yet the intellect does so when it reflects on its own work; accordingly, some sciences are about things, and others are about intentions understood. Now, that the intention understood is not the very intellect within us is clear from this: The act of being of the intention understood consists in its very being understood; the being of our intellect does not so consist; its being is not its act of understanding.
[7] Since in God, therefore, being and understanding are identical, the intention understood in Him is His very intellect. And because understanding in Him is the thing understood (for by understanding Himself He understands all other things, as was shown in Book I), it follows that in God, because He understands Himself, the intellect, the thing understood, and the intention understood are all identical.