The main principles of angelic knowledge have now been set forth; and Thomas pauses to point out to what extent the angels know the future, the secret thoughts of our hearts, and the mysteries of grace. He has still to consider the mode and measure of the angelic knowledge from other points of view. Whatever the angels may know through their implanted natures, they know perfectly (actu); but it may be otherwise as to what is divinely revealed to them. What they know, they know without the need of argument. And the discussion closes with remarks on Augustine’s phrase and conception of the matutina and vespertina knowledge of angels: the former being the knowledge of things as they are in the Word; the latter being the knowledge of things as they are in their own natures.[603]
V
That the abstract and the universal is the noble and delectable, we learn from this exposition of angelic knowledge. We may learn the same from Thomas’s presentation of the modes and contents of human understanding. The Summa theologiae follows the Scriptural order of presentation;[604] which is doubtless the reason why Thomas, instead of passing from immaterial creatures to the partly immaterial creature man, considers first the creation of physical things—the Scriptural work of the six days. After this he takes up the last act of the Creation—man. In the Summa he considers man so far as his composite nature comes within the scope of theology. Accordingly the principal topic is the human soul (anima); and the body is regarded only in relation to the soul, its qualities and its fate. Thomas will follow Dionysius (Pseudo-Areopagite) in considering first the nature (essentia) of the soul, then its faculties (virtus sive potentiae), and thirdly, its mode of action (operatio).
Under the first head he argues (Pars prima, Qu. lxxv.) that the soul, which is the primum principium of life, is not body, but the body’s consummation (actus) and forma. Further, inasmuch as the soul is the principium of mental action, it must be an incorporeal principle existing by itself. It cannot properly be said to be the man; for man is not soul alone, but a composite of soul and body. But the soul, being immaterial and intellectual, is not a composite of form and matter. It is not subject to corruption. Concerning its union with the body (Qu. lxxvi.), “it is necessary to say that the mind (intellectus), which is the principle of intellectual action, is the form (forma) of the human body.” One and the same intellectual principle does not pertain to all human bodies: there is no common human soul, but as many souls as there are men.[605] Yet no man has a plurality of souls. “If indeed the anima intellectiva were not united to the body as form, but only as motor (as the Platonists affirm), it would be necessary to find in man another substantial form, through which the body should be set in its being. But if, as we have shown, the soul is united to the body as substantial form, there cannot be another substantial form beside it” (Qu. lxxvi. Art. 4). The human soul is fitly joined to its body; for it holds the lowest grade among intellectual substances, having no knowledge of truth implanted in it, as the angels have; it has to gather knowledge per viam sensus. “But nature never omits what is necessary. Hence the anima intellectiva must have not only the faculty of knowing, but the faculty of feeling (sentiendi). Sense-action can take place only through a corporeal instrument. Therefore the anima intellectiva ought to be united to such a body, which should be to it a convenient organ of sense” (Art. 5). Moreover, “since the soul is united to the body as form, it is altogether in any and every part of the body” (Art. 8).
It is a cardinal point (Qu. lxxvii.) with Thomas that the soul’s essentia is not its potentia: the soul is not its faculties. That is true only of God. In Him there is no diversity. There is some diversity of faculty in an angel; and more in man, a creature on the confines of the corporeal and spiritual creation, in whom concur the powers of both. There is order and priority among the powers of the soul: the potentiae intellectivae are higher than the potentiae sensitivae, and control them; while the latter are above the potentiae nutritivae. Yet the order of their generation is the reverse. The highest of the sensitive faculties is sight. The anima is the subject in which are the powers of knowing and willing (potentiae intellectivae); but the subject in which are the powers of sensation is the combination of the soul and body. All the powers of the soul, whether the subject be soul alone or soul and body, flow from the essence of the soul, as from a source (principium).
Thomas follows (Qu. lxxviii.) Aristotle in dividing the powers of the soul into vegetative, sensitive, appetitive, motor, and intellectual. In taking up the last, he points out (Qu. lxxix.) that intelligence (intellectus) is a power of the soul, and not the soul itself. He then follows the Philosopher in showing how intelligence (intelligere) is to be regarded as a passive power, and he presents the difficult Aristotelian device of the intellectus agens, and argues that memory and reason are not to be regarded as powers distinct from the intelligence (intellectus).
How does the soul, while united to the body (the anima conjuncta), (1) know corporeal things which are beneath it? (2) how does it know itself and what is in itself? and (3) how does it know immaterial substances which are above it? The exposition of these problems is introduced by (Qu. lxxxiv.) a historical discussion of the primi philosophi who thought there was nothing but body in the world. Then came Plato, seeking “to save some certain cognition of truth” by means of his theory of Ideas. But Plato seems to have erred in thinking that the form of the known must be in the knower as it is in the known. This is not necessary. In sense-perception the form of the thing is not in sense as it is in the thing. “And likewise the intelligence receives the species (Ideas) of material and mobile bodies immaterially and immutably, after its own mode; for the received is in the recipient after the mode of the recipient. Hence it is to be held that the soul through the intelligence knows bodies by immaterial, universal, and necessary cognition.”
Thomas sets this matter forth in a manner very illuminating as to his general position regarding knowledge:
“It follows that material things which are known must exist in the knower, not materially, but immaterially. And the reason of this is that the act of cognition extends itself to those things which are outside of the knower. For we know things outside of us. But through matter, the form of the thing is limited to what is single (aliquid unum). Hence it is plain that the ratio (proper nature) of cognition is the opposite of the ratio of materiality. And therefore things, like plants, which receive forms only materially, are in no way cognoscitivae, as is said in the second book of De anima. The more immaterially anything possesses the form of the thing known, the more perfectly it knows. Wherefore the intelligence, which abstracts the species (Idea) not only from matter, but also from individualizing material conditions, knows more perfectly than sense, which receives the form of the thing known without matter indeed, but with material conditions. Among the senses themselves, sight is the most cognoscitivus, because least material. And among intelligences, that is the more perfect which is the more immaterial” (Qu. lxxxiv. Art. 2).
Then Thomas again differs from Plato, and holds with Aristotle, that the intelligence through which the soul knows has not its ideas written upon it by nature, but from the first is capable of receiving them all (sed est in principio in potentia ad hujusmodi species omnes). Hereupon, and with further arguments, Thomas shows “that the species intelligibiles, by which our soul knows, do not arise from separate forms” or ideas.