"A separately subsistent intelligence," writes St Thomas (Chap. XLI), "by knowing its own essence, knows both what is above it and what is below it, particularly if what is above it is also its cause, since the likeness of the cause must be found in the effect. Hence, since God is the cause of all created subsistent intelligences, they, by knowing their own essences, know by some sort of vision (per modum visionis cujusdam) even God Himself: for a thing is known by intellect in a manner of vision, when its likeness exists in intellect: whatever intellect then apprehends a separately subsistent intelligence, and knows the same in its essential nature, sees God in a higher way than is possible by any of the modes of cognition already mentioned." Know an angel, then, or pure spirit, in his essence, and you will thereby have a higher knowledge of God than any that you could attain by any other speculation of science or philosophy. Consequently, if the knowledge of God be happiness, happiness, it seems, will best open to us men, if we can find some method of reading the innermost natures of angels. Alexander of Aphrodisias (fl A.D. 200), Avempace (Ibn-Badja, d. 1138), and Averroes (Ibn-Roschd, d. 1198), each was quoted in St Thomas's day as the author of a method enabling men to do this, methods which St Thomas elaborately confutes in these chapters.
Avempace's plan was to study the speculative sciences, and thence forming abstract generalisations, one higher than the other, -- or perhaps he meant (what is by no means the same thing) one fuller of 'content' than the other, -- to ascend to the cognition of pure intelligence. St Thomas describes the process in scholastic terms, thus; "to extract the quiddity of everything which is not its own quiddity; and if that quiddity has a quiddity, again to abstract the quiddity of that quiddity, till we come to a stand somewhere, arriving by the method of analysis at the knowledge of the quiddity of a being, subsisting apart, which has not another quiddity" (Chap. XLI): which words perhaps need some explanation. "The quiddity of a thing which is not its own quiddity" means then an essence, or essential quality, which is shared by many subjects, and is not all embodied in one subject, constituting that subject entirely. Thus prudence is in Cato, and in many others besides. Cato is not all prudence: he is not the embodiment of sheer prudence and nothing else. Prudence then in Cato is a quiddity which is not its own quiddity. St Thomas well observes that Avempace's method is Platonic Idealism revived. He adds that, starting as our abstractions must, from sensible objects, we can never attain to a view of the essential nature of a pure spirit. "If by understanding of the natures and quiddities of sensible things, we arrive at an understanding of separately subsistent intelligences, that understanding of such intelligences must be reached through some one of the speculative sciences. But we do not see how this is to be done: for there is no speculative science which teaches concerning any one of the separately subsistent intelligences what it is in essence, but only the fact of its existence" (Chap. XLI).
-- Averroes, as might have been expected, proceeds upon his favourite notion of the continuatio, or conjunction of the individual mind with the one vast intelligence, active and potential, that is without (B. II, Chap. LX). St Thomas's summary of the Commentator's views ends thus -- (it is a very free paraphrase of Averroes's words as they appear in the Latin of the Venice edition of 1574, pp. 186, 187): "This perfect progress towards conjunction with the supreme intelligence comes of zealous study of the speculative sciences, whereby true intellectual notions are acquired, and false opinions are excluded, such opinions lying beyond the line of this progress, like monstrous births outside of the line of the operation of nature. To this advance men help one another by helping one another in the speculative sciences. When then all things now potentially intelligible come to be in us actually understood, then the active intellect: will be perfectly conjoined with us as a form, and we shall understand by it perfectly. Hence, since it belongs to the active intellect to understand substances existing apart, we shall then understand those separately subsistent beings as we now understand the notions of speculative science; and this will be man's final happiness, in which man shall be as a god" (Chap. XLIII).
If any one used such language in our time, we should understand him to mean by continuatio, or union with the supreme intelligence, as regards the individual, his instruction up to the level of the science of his age; and as regards the age itself, the maintenance of the level of science reached by the previous generation, and the further raising of that level. But it is not safe to make out an ancient author to have meant exactly what his words would mean, if spoken now. St Thomas gives a reference to the commentary of Averroes on Aristotle, De anima, III, a reference which I have duly followed up. I find that Averroes quotes Alexander and Avempace, disagreeing with them both. St Thomas, I believe, is indebted to Averroes for his knowledge of Alexander and Avempace. Now nowhere in Averroes, nor in either of the two authors whom he quotes, do I find any reference whatever to separate substances personified as thinking intelligences, or angels, -- nor, for that matter, in Aristotle either. The discussion had its origin in an unfulfilled promise of Aristotle (De Anima III, vii, 10) to enquire, ara endechetai tôn kechôrismenôn to noein onta auton mê kechôrismenon megethous; (is it possible for the mind, without being itself separate from extended body, to understand any of the things that are so separated?) To interpret ta kechôrismena to mean 'pure spirits' seems going a long way beyond Aristotle, who probably meant no more than 'products of high abstraction': nor did Averroes, commenting on the third book of the De anima, or Alexander, or Avempace, as quoted in that commentary, mean anything more. The transformation of these high abstractions (kechôrismena) into thinking beings, pure spirits, or angels, was, I conjecture, the work of the Neo-Averroists, whom St Thomas encountered at the University of Paris. It is with these Averroists, not with Averroes him self, that St Thomas mainly contends in these chapters. The argument is intricate, the theory which it impugns obsolete, nor is it worth while further to detain the modern reader with the discussion. No man now living expects to 'pick the brains' of angels, and so find happiness in this life by sharing an angel's natural knowledge of God. Nor did Averroes, so far as his comments on the De anima show, dream of anything so absurd.
Lest any one should think the expression 'to pick the brains of angels' a travesty, I quote the Latin of St Thomas: Si igitur per cognitionem intellectivam, quae est ex phantasmatibus, possit pervenire aliquis nostrum ad intelligendas substantias separatas, possibile erit quod aliquis in hac vita intelligat ipsas substantias separatas, et per consequens videndo ipsas substantias separatas participabis modum illius cognitionis quo substantia separata intelligens se intelligit Deum (Chap. XLI).
This is the translation: "If then by intellectual knowledge, got out of impressions on the phantasy, any one of us could arrive to understand subsistent beings existing apart [i.e., pure spirits], it would be possible for one in this life to understand those same pure spirits, and consequently by seeing [in his mind's eye] those pure spirits he would share in the mode of that knowledge whereby a pure spirit, understanding itself, understands God." I need hardly remind the reader that St Thomas himself rejects this notion, and is, I think, mistaken in attributing it to Averroes.
Of God and His Creatures: 3.41