Objection 1: It would seem that the angel's intellect is sometimes in potentiality and sometimes in act. For movement is the act of what is in potentiality, as stated in Phys. iii, 6. But the angels' minds are moved by understanding, as Dionysius says (Div. Nom. iv). Therefore the angelic minds are sometimes in potentiality.

Objection 2: Further, since desire is of a thing not possessed but possible to have, whoever desires to know anything is in potentiality thereto. But it is said (1 Pt. 1:12): "On Whom the angels desire to look." Therefore the angel's intellect is sometimes in potentiality.

Objection 3: Further, in the book De Causis it is stated that "an intelligence understands according to the mode of its substance." But the angel's intelligence has some admixture of potentiality. Therefore it sometimes understands potentially.

On the contrary, Augustine says (Gen. ad lit. ii): "Since the angels were created, in the eternity of the Word, they enjoy holy and devout contemplation." Now a contemplating intellect is not in potentiality, but in act. Therefore the intellect of an angel is not in potentiality.

I answer that, As the Philosopher states (De Anima iii, text. 8; Phys. viii, 32), the intellect is in potentiality in two ways; first, "as before learning or discovering," that is, before it has the habit of knowledge; secondly, as "when it possesses the habit of knowledge, but does not actually consider." In the first way an angel's intellect is never in potentiality with regard to the things to which his natural knowledge extends. For, as the higher, namely, the heavenly, bodies have no potentiality to existence, which is not fully actuated, in the same way the heavenly intellects, the angels, have no intelligible potentiality which is not fully completed by connatural intelligible species. But with regard to things divinely revealed to them, there is nothing to hinder them from being in potentiality: because even the heavenly bodies are at times in potentiality to being enlightened by the sun.

In the second way an angel's intellect can be in potentiality with regard to things learnt by natural knowledge; for he is not always actually considering everything that he knows by natural knowledge. But as to the knowledge of the Word, and of the things he beholds in the Word, he is never in this way in potentiality; because he is always actually beholding the Word, and the things he sees in the Word. For the bliss of the angels consists in such vision; and beatitude does not consist in habit, but in act, as the Philosopher says (Ethic. i, 8).

Reply to Objection 1: Movement is taken there not as the act of something imperfect, that is, of something existing in potentiality, but as the act of something perfect, that is, of one actually existing. In this way understanding and feeling are termed movements, as stated in De Anima iii, text. 28.

Reply to Objection 2: Such desire on the part of the angels does not exclude the object desired, but weariness thereof. Or they are said to desire the vision of God with regard to fresh revelations, which they receive from God to fit them for the tasks which they have to perform.

Reply to Objection 3: In the angel's substance there is no potentiality divested of act. In the same way, the angel's intellect is never so in potentiality as to be without act.

Objection 1: It would seem that an angel cannot understand many things at the same time. For the Philosopher says (Topic. ii, 4) that "it may happen that we know many things, but understand only one."

Objection 2: Further, nothing is understood unless the intellect be informed by an intelligible species; just at the body is formed by shape. But one body cannot be formed into many shapes. Therefore neither can one intellect simultaneously understand various intelligible things.

Objection 3: Further, to understand is a kind of movement. But no movement terminates in various terms. Therefore many things cannot be understood altogether.

On the contrary, Augustine says (Gen. ad lit. iv, 32): "The spiritual faculty of the angelic mind comprehends most easily at the same time all things that it wills."

I answer that, As unity of term is requisite for unity of movement, so is unity of object required for unity of operation. Now it happens that several things may be taken as several or as one; like the parts of a continuous whole. For if each of the parts be considered severally they are many: consequently neither by sense nor by intellect are they grasped by one operation, nor all at once. In another way they are taken as forming one in the whole; and so they are grasped both by sense and intellect all at once and by one operation; as long as the entire continuous whole is considered, as is stated in De Anima iii, text. 23. In this way our intellect understands together both the subject and the predicate, as forming parts of one proposition; and also two things compared together, according as they agree in one point of comparison. From this it is evident that many things, in so far as they are distinct, cannot be understood at once; but in so far as they are comprised under one intelligible concept, they can be understood together. Now everything is actually intelligible according as its image is in the intellect. All things, then, which can be known by one intelligible species, are known as one intelligible object, and therefore are understood simultaneously. But things known by various intelligible species, are apprehended as different intelligible objects.

Consequently, by such knowledge as the angels have of things through the Word, they know all things under one intelligible species, which is the Divine essence. Therefore, as regards such knowledge, they know all things at once: just as in heaven "our thoughts will not be fleeting, going and returning from one thing to another, but we shall survey all our knowledge at the same time by one glance," as Augustine says (De Trin. xv, 16). But by that knowledge wherewith the angels know things by innate species, they can at one time know all things which can be comprised under one species; but not such as are under various species.

Reply to Objection 1: To understand many things as one, is, so to speak, to understand one thing.

Reply to Objection 2: The intellect is informed by the intelligible species which it has within it. So it can behold at the same time many intelligible objects under one species; as one body can by one shape be likened to many bodies.

To the third objection the answer is the same as the first.

Objection 1: It would seem that the knowledge of an angel is discursive. For the discursive movement of the mind comes from one thing being known through another. But the angels know one thing through another; for they know creatures through the Word. Therefore the intellect of an angel knows by discursive method.

Objection 2: Further, whatever a lower power can do, the higher can do. But the human intellect can syllogize, and know causes in effects; all of which is the discursive method. Therefore the intellect of the angel, which is higher in the order of nature, can with greater reason do this.

Objection 3: Further, Isidore (De sum. bono i, 10) says that "demons learn more things by experience." But experimental knowledge is discursive: for, "one experience comes of many remembrances, and one universal from many experiences," as Aristotle observes (Poster. ii; Metaph. vii). Therefore an angel's knowledge is discursive.

On the contrary, Dionysius says (Div. Nom. vii) that the "angels do not acquire Divine knowledge from separate discourses, nor are they led to something particular from something common."

I answer that, As has often been stated (Article [1]; Question [55], Article [1]), the angels hold that grade among spiritual substances which the heavenly bodies hold among corporeal substances: for Dionysius calls them "heavenly minds" (Article [1]; Question [55], Article [1]). Now, the difference between heavenly and earthly bodies is this, that earthly bodies obtain their last perfection by chance and movement: while the heavenly bodies have their last perfection at once from their very nature. So, likewise, the lower, namely, the human, intellects obtain their perfection in the knowledge of truth by a kind of movement and discursive intellectual operation; that is to say, as they advance from one known thing to another. But, if from the knowledge of a known principle they were straightway to perceive as known all its consequent conclusions, then there would be no discursive process at all. Such is the condition of the angels, because in the truths which they know naturally, they at once behold all things whatsoever that can be known in them.

Therefore they are called "intellectual beings": because even with ourselves the things which are instantly grasped by the mind are said to be understood [intelligi]; hence "intellect" is defined as the habit of first principles. But human souls which acquire knowledge of truth by the discursive method are called "rational"; and this comes of the feebleness of their intellectual light. For if they possessed the fulness of intellectual light, like the angels, then in the first aspect of principles they would at once comprehend their whole range, by perceiving whatever could be reasoned out from them.

Reply to Objection 1: Discursion expresses movement of a kind. Now all movement is from something before to something after. Hence discursive knowledge comes about according as from something previously known one attains to the knowledge of what is afterwards known, and which was previously unknown. But if in the thing perceived something else be seen at the same time, as an object and its image are seen simultaneously in a mirror, it is not discursive knowledge. And in this way the angels know things in the Word.

Reply to Objection 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.

Reply to Objection 3: Experience is affirmed of angels and demons simply by way of similitude, forasmuch as they know sensible things which are present, yet without any discursion withal.

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.

Objection 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 (Article [2]). Therefore he must know affirmation and negation by diverse species. And so it seems that he understands by composing and dividing.

Objection 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 (Article [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 to Objection 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 to Objection 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 to Objection 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.

Objection 2: Further, nescience is the cause of estimating falsely. But, as Dionysius says (Eccl. Hier. vi), there can be nescience in the angels. Therefore it seems there can be falsehood in them.

Objection 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 (Questions. 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 (Article [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.

Objection 1: It would seem that there is neither an evening nor a morning knowledge in the angels; because evening and morning have an admixture of darkness. But there is no darkness in the knowledge of an angel; since there is no error nor falsehood. Therefore the angelic knowledge ought not to be termed morning and evening knowledge.

Objection 2: Further, between evening and morning the night intervenes; while noonday falls between morning and evening. Consequently, if there be a morning and an evening knowledge in the angels, for the same reason it appears that there ought to be a noonday and a night knowledge.

Objection 3: Further, knowledge is diversified according to the difference of the objects known: hence the Philosopher says (De Anima iii, text. 38), "The sciences are divided just as things are." But there is a threefold existence of things: to wit, in the Word; in their own natures; and in the angelic knowledge, as Augustine observes (Gen. ad lit. ii, 8). If, therefore, a morning and an evening knowledge be admitted in the angels, because of the existence of things in the Word, and in their own nature, then there ought to be admitted a third class of knowledge, on account of the existence of things in the angelic mind.

On the contrary, Augustine (Gen. ad lit. iv, 22,31; De Civ. Dei xii, 7,20) divides the knowledge of the angels into morning and evening knowledge.

I answer that, The expression "morning" and "evening" knowledge was devised by Augustine; who interprets the six days wherein God made all things, not as ordinary days measured by the solar circuit, since the sun was only made on the fourth day, but as one day, namely, the day of angelic knowledge as directed to six classes of things. As in the ordinary day, morning is the beginning, and evening the close of day, so, their knowledge of the primordial being of things is called morning knowledge; and this is according as things exist in the Word. But their knowledge of the very being of the thing created, as it stands in its own nature, is termed evening knowledge; because the being of things flows from the Word, as from a kind of primordial principle; and this flow is terminated in the being which they have in themselves.

Reply to Objection 1: Evening and morning knowledge in the angelic knowledge are not taken as compared to an admixture of darkness, but as compared to beginning and end. Or else it can be said, as Augustine puts it (Gen. ad lit. iv, 23), that there is nothing to prevent us from calling something light in comparison with one thing, and darkness with respect to another. In the same way the life of the faithful and the just is called light in comparison with the wicked, according to Eph. 5:8: "You were heretofore darkness; but now, light in the Lord": yet this very life of the faithful, when set in contrast to the life of glory, is termed darkness, according to 2 Pt. 1:19: "You have the firm prophetic word, whereunto you do well to attend, as to a light that shineth in a dark place." So the angel's knowledge by which he knows things in their own nature, is day in comparison with ignorance or error; yet it is dark in comparison with the vision of the Word.

Reply to Objection 2: The morning and evening knowledge belong to the day, that is, to the enlightened angels, who are quite apart from the darkness, that is, from the evil spirits. The good angels, while knowing the creature, do not adhere to it, for that would be to turn to darkness and to night; but they refer this back to the praise of God, in Whom, as in their principle, they know all things. Consequently after "evening" there is no night, but "morning"; so that morning is the end of the preceding day, and the beginning of the following, in so far as the angels refer to God's praise their knowledge of the preceding work. Noonday is comprised under the name of day, as the middle between the two extremes. Or else the noon can be referred to their knowledge of God Himself, Who has neither beginning nor end.

Reply to Objection 3: The angels themselves are also creatures. Accordingly the existence of things in the angelic knowledge is comprised under evening knowledge, as also the existence of things in their own nature.

Objection 1: It would seem that the morning and the evening knowledge are one. For it is said (Gn. 1:5): "There was evening and morning, one day." But by the expression "day" the knowledge of the angels is to be understood, as Augustine says (Gen. ad lit. iv, 23). Therefore the morning and evening knowledge of the angels are one and the same.

Objection 2: Further, it is impossible for one faculty to have two operations at the same time. But the angels are always using their morning knowledge; because they are always beholding God and things in God, according to Mt. 18:10. Therefore, if the evening knowledge were different from the morning, the angel could never exercise his evening knowledge.

Objection 3: Further, the Apostle says (1 Cor. 13:10): "When that which is perfect is come, then that which is in part shall be done away." But, if the evening knowledge be different from the morning, it is compared to it as the less perfect to the perfect. Therefore the evening knowledge cannot exist together with the morning knowledge.

On the contrary, Augustine says (Gen. ad lit. iv, 24): "There is a vast difference between knowing anything as it is in the Word of God, and as it is in its own nature; so that the former belongs to the day, and the latter to the evening."

I answer that, As was observed (Article [6]), the evening knowledge is that by which the angels know things in their proper nature. This cannot be understood as if they drew their knowledge from the proper nature of things, so that the preposition "in" denotes the form of a principle; because, as has been already stated (Question [55], Article [2]), the angels do not draw their knowledge from things. It follows, then, that when we say "in their proper nature" we refer to the aspect of the thing known in so far as it is an object of knowledge; that is to say, that the evening knowledge is in the angels in so far as they know the being of things which those things have in their own nature.

Now they know this through a twofold medium, namely, by innate ideas, or by the forms of things existing in the Word. For by beholding the Word, they know not merely the being of things as existing in the Word, but the being as possessed by the things themselves; as God by contemplating Himself sees that being which things have in their own nature. It, therefore, it be called evening knowledge, in so far as when the angels behold the Word, they know the being which things have in their proper nature, then the morning and the evening knowledge are essentially one and the same, and only differ as to the things known. If it be called evening knowledge, in so far as through innate ideas they know the being which things have in their own natures, then the morning and the evening knowledge differ. Thus Augustine seems to understand it when he assigns one as inferior to the other.

Reply to Objection 1: The six days, as Augustine understands them, are taken as the six classes of things known by the angels; so that the day's unit is taken according to the unit of the thing understood; which, nevertheless, can be apprehended by various ways of knowing it.

Reply to Objection 2: There can be two operations of the same faculty at the one time, one of which is referred to the other; as is evident when the will at the same time wills the end and the means to the end; and the intellect at the same instant perceives principles and conclusions through those principles, when it has already acquired knowledge. As Augustine says (Gen. ad lit. iv, 24), the evening knowledge is referred to the morning knowledge in the angels; hence there is nothing to hinder both from being at the same time in the angels.

Reply to Objection 3: On the coming of what is perfect, the opposite imperfect is done away: just as faith, which is of the things that are not seen, is made void when vision succeeds. But the imperfection of the evening knowledge is not opposed to the perfection of the morning knowledge. For that a thing be known in itself, is not opposite to its being known in its cause. Nor, again, is there any inconsistency in knowing a thing through two mediums, one of which is more perfect and the other less perfect; just as we can have a demonstrative and a probable medium for reaching the same conclusion. In like manner a thing can be known by the angel through the uncreated Word, and through an innate idea.