Summa Theologica, Part I (Prima Pars) From the Complete...

Reply Obj. 2: The angels can syllogize, in the sense of knowing a syllogism; and they see effects in causes, and causes in effects: yet they do not acquire knowledge of an unknown truth in this way, by syllogizing from causes to effect, or from effect to cause.

Objection 1: It would seem that the angels understand by composing and dividing. For, where there is multiplicity of things understood, there is composition of the same, as is said in De Anima iii, text. 21. But there is a multitude of things understood in the angelic mind; because angels apprehend different things by various species, and not all at one time. Therefore there is composition and division in the angel's mind.

Obj. 2: Further, negation is far more remote from affirmation than any two opposite natures are; because the first of distinctions is that of affirmation and negation. But the angel knows certain distant natures not by one, but by diverse species, as is evident from what was said (A. 2). Therefore he must know affirmation and negation by diverse species. And so it seems that he understands by composing and dividing.

Obj. 3: Further, speech is a sign of the intellect. But in speaking to men, angels use affirmative and negative expressions, which are signs of composition and of division in the intellect; as is manifest from many passages of Sacred Scripture. Therefore it seems that the angel understands by composing and dividing.

On the contrary, Dionysius says (Div. Nom. vii) that "the intellectual power of the angel shines forth with the clear simplicity of divine concepts." But a simple intelligence is without composition and division. Therefore the angel understands without composition or division.

I answer that, As in the intellect, when reasoning, the conclusion is compared with the principle, so in the intellect composing and dividing, the predicate is compared with the subject. For if our intellect were to see at once the truth of the conclusion in the principle, it would never understand by discursion and reasoning. In like manner, if the intellect in apprehending the quiddity of the subject were at once to have knowledge of all that can be attributed to, or removed from, the subject, it would never understand by composing and dividing, but only by understanding the essence. Thus it is evident that for the self-same reason our intellect understands by discursion, and by composing and dividing, namely, that in the first apprehension of anything newly apprehended it does not at once grasp all that is virtually contained in it. And this comes from the weakness of the intellectual light within us, as has been said (A. 3). Hence, since the intellectual light is perfect in the angel, for he is a pure and most clear mirror, as Dionysius says (Div. Nom. iv), it follows that as the angel does not understand by reasoning, so neither does he by composing and dividing.

Nevertheless, he understands the composition and the division of enunciations, just as he apprehends the reasoning of syllogisms: for he understands simply, such things as are composite, things movable immovably, and material things immaterially.

Reply Obj. 1: Not every multitude of things understood causes composition, but a multitude of such things understood that one of them is attributed to, or denied of, another. When an angel apprehends the nature of anything, he at the same time understands whatever can be either attributed to it, or denied of it. Hence, in apprehending a nature, he by one simple perception grasps all that we can learn by composing and dividing.

Reply Obj. 2: The various natures of things differ less as to their mode of existing than do affirmation and negation. Yet, as to the way in which they are known, affirmation and negation have something more in common; because directly the truth of an affirmation is known, the falsehood of the opposite negation is known also.

Reply Obj. 3: The fact that angels use affirmative and negative forms of speech, shows that they know both composition and division: yet not that they know by composing and dividing, but by knowing simply the nature of a thing. _______________________

Objection 1: It would seem that there can be falsehood in the angel's intellect. For perversity appertains to falsehood. But, as Dionysius says (Div. Nom. iv), there is "a perverted fancy" in the demons. Therefore it seems that there can be falsehood in the intellect of the angels.

Obj. 3: Further, everything which falls short of the truth of wisdom, and which has a depraved reason, has falsehood or error in its intellect. But Dionysius (Div. Nom. vii) affirms this of the demons. Therefore it seems that there can be error in the minds of the angels.

On the contrary, The Philosopher says (De Anima iii, text. 41) that "the intelligence is always true." Augustine likewise says (QQ. 83, qu. 32) that "nothing but what is true can be the object of intelligence" Therefore there can be neither deception nor falsehood in the angel's knowledge.

I answer that, The truth of this question depends partly upon what has gone before. For it has been said (A. 4) that an angel understands not by composing and dividing, but by understanding what a thing is. Now the intellect is always true as regards what a thing is, just as the sense regarding its proper object, as is said in De Anima iii, text. 26. But by accident, deception and falsehood creep in, when we understand the essence of a thing by some kind of composition, and this happens either when we take the definition of one thing for another, or when the parts of a definition do not hang together, as if we were to accept as the definition of some creature, "a four-footed flying beast," for there is no such animal. And this comes about in things composite, the definition of which is drawn from diverse elements, one of which is as matter to the other. But there is no room for error in understanding simple quiddities, as is stated in Metaph. ix, text. 22; for either they are not grasped at all, and so we know nothing respecting them; or else they are known precisely as they exist.

So therefore, no falsehood, error, or deception can exist of itself in the mind of any angel; yet it does so happen accidentally; but very differently from the way it befalls us. For we sometimes get at the quiddity of a thing by a composing and dividing process, as when, by division and demonstration, we seek out the truth of a definition. Such is not the method of the angels; but through the (knowledge of the) essence of a thing they know everything that can be said regarding it. Now it is quite evident that the quiddity of a thing can be a source of knowledge with regard to everything belonging to such thing, or excluded from it; but not of what may be dependent on God's supernatural ordinance. Consequently, owing to their upright will, from their knowing the nature of every creature, the good angels form no judgments as to the nature of the qualities therein, save under the Divine ordinance; hence there can be no error or falsehood in them. But since the minds of demons are utterly perverted from the Divine wisdom, they at times form their opinions of things simply according to the natural conditions of the same. Nor are they ever deceived as to the natural properties of anything; but they can be misled with regard to supernatural matters; for example, on seeing a dead man, they may suppose that he will not rise again, or, on beholding Christ, they may judge Him not to be God.

From all this the answers to the objections of both sides of the question are evident. For the perversity of the demons comes of their not being subject to the Divine wisdom; while nescience is in the angels as regards things knowable, not naturally but supernaturally. It is, furthermore, evident that their understanding of what a thing is, is always true, save accidentally, according as it is, in an undue manner, referred to some composition or division. _______________________