De veritate EN 72



In seeing His own essence, God knows some things, namely, the present, past, and future, will the knowledge of vision. Other things, namely, all those which He could make but which nevertheless do not exist, have not existed, and will not exist—these He knows will the knowledge of simple understanding. Now, it seems impossible that any creature seeing the divine essence should know all the things which God knows will His knowledge of simple understanding.

It is clear that the number of effects a person knows of a cause is in proportion to the perfection of his knowledge of that cause. For example, the more perfectly one knows a principle of demonstration, the more conclusions can he draw from it. Consequently, if an intellect is to know from its knowledge of a cause all the effects of that cause, it must attain a perfect knowledge of it and, consequently, must comprehend it. Now, as is evident from what has been said previously, it is impossible for a created intellect to comprehend the divine essence. Therefore, it is impossible for any created intellect in seeing the divine essence to know all the things that can be caused by it.

However, it is possible for a created intellect which sees God to know all that God knows will His knowledge of vision. Ail hold this is true of the soul of Christ. Opinion is split, however, about the others who see God through His essence. Some say that all angels and all the souls of the blessed necessarily know all things by seeing God’s essence because they are like men who look into a mirror and see all that is reflected there. This opinion, however, seems to contradict the sayings of the saints, especially those of Dionysius, who expressly states that the lower angels rid themselves of their ignorance by the help of higher angels. Hence, we must assert that the higher angels know things of which the lower are ignorant, even though all angels without exception contemplate God.

Consequently, we answer that things do not exist in the divine essence as actually distinct; but, as Dionysius says, in God all things are one in the way in which many effects are united in one cause. Images reflected in a mirror, however, are actually distinct; consequently, the way in which all things are in the divine essence is more like the way in which effects are in a cause than that in which images are in a mirror. Moreover, one who knows a cause will know all the effects which that cause can produce only if he comprehends that cause, but such comprehension is impossible for a created intellect will regard to the divine essence. Hence, in seeing His essence God alone necessarily knows all the things that He can make. The same is true of the effects that can be produced by the divine essence: one knows more of these the more fully he sees God’s essence. Consequently, the soul of Christ, which sees God more perfectly than all other creatures do, is said to know all things, present, past, and future. Other creatures, however, do not have this knowledge. Each one of them sees more or fewer effects of God in proportion to the knowledge he has of Him.

Answers to Difficulties:

1. As Peter Lombard points out, when one says that angels see all things in the Word before they come into being, his statement should not be understood as referring to all angels, but possibly only to the higher angels. Nor do these see all things perfectly, but, perhaps, only in general. Some things they know, as it were, only implicitly. Or one could also reply that many concepts can be drawn from one object, just as many demonstrations can be made about a triangle; and it is possible for one to know the definition of a triangle and still not know all the things that can be known about a triangle. Therefore, it is one thing to know all things, and another to know all that can be known about things.

However, it is sufficiently probable that all who see God through His essence know all creatures at least according to their species. This is what Isidore means when he says angels "know all- things in the Word before they come into existence," for coming into existence pertains to things, not to intelligible characters. It is not necessary, however, that an angel know all the intelligible characters of a thing when he knows it; and, even if he were to know all the natural properties which can be known by comprehending its essence, he would not know it according to all the formalities by which it falls under the ordering of divine providence, which ordains one thing to many events. It is about such things that the highest angels enlighten the lower. And this is what Dionysius means when he says that higher angels teach the lower about the intelligible characters of things.

2. That argument holds when sight is joined to a likeness according to the entire potentialities of that likeness. Then sight necessarily knows everything to which the likeness extends. However, a created intellect is not joined to the divine essence in this manner. Consequently, the argument does not hold.

3. The fact that an angel, seeing God, nevertheless does not see all things is due to a defect in his intellect, which is not united to the divine essence according to the total cognoscibility of the essence. But, as mentioned above, this defect is not contrary to the purity of the angelic intellect.

4. The ambit of a soul’s natural power includes only those objects which can be understood by the light of the active intellect, and these are forms abstracted from sensible objects. Similarly, the natural power of an angelic intellect includes only those objects that are manifested to it by its own natural light, which is not, however, sufficient to manifest all the things hidden in the wisdom of God. Moreover, the soul receives knowledge of those things which it can know naturally only through a medium that is proportioned to itself. Consequently, even though two persons may apprehend a conclusion by one and the same medium, one will come to know it when the other, will a slower intellect, will not. Similarly, when angels see God’s essence, a higher angel will know many things which a lower angel will not. However, the lower angel gets knowledge of these things through a medium that is more proportioned to Mm, namely, the light of the higher angel. Hence, it is necessary for one angel to enlighten another.

5. Affection tends toward things themselves, but intellect not only tends toward things but also divides them up into many concepts. Consequently, these concepts are understood but not loved. They can, however, be the principle of love or the reason for it. But, properly speaking, what is loved is the thing itself. Therefore, since the angels who see God through His essence know all creatures, they can love all creatures. But, because they do not apprehend all the intelligible aspects of creatures, they do not love creatures under all the aspects under which they can be loved.

6. Even though God is at an infinite distance from the angelic intellect, angels do not know God according to the mode of Him infinity, because they do not know Him infinitely. Consequently, it is not necessary that they know all the infinite things that He knows.

7. God could reveal to a person in this life so many things that he would know more about creatures than the intellect of one in heaven knows. Similarly, God could reveal to a person in a lower place in heaven as many things as one in a higher place knows—or even more things. But this is not the point of our present inquiry. The point is:

Does it follow that a created intellect knows all things from the fact that it sees God’s essence?

8. Gregory’s statement can be understood as referring to things that pertain to the substance of beatitude. Or one can reply that Gregory is speaking about the sufficiency of the medium, because the divine essence is a medium that is sufficient to make all things known. Gregory accordingly holds that it is not strange if one who sees the divine essence knows future things; but that he does not know all things comes from a defect in the intellect which does not comprehend it.

9. This statement declares that every creature is small for a soul seeing the divine essence; that is, from such a soul no creature is hidden because of its nobility. There can be another reason, however, why it might remain hidden, namely, the f act that it is not joined to the soul by a proportionate medium through which the soul could know it.

10. That argument would hold if a physical eye could take upon itself all the potentialities of physical light. In the problem proposed, this is clearly not the case.

11. When an intellect touches God by its cognition, it knows the whole of God, even though it does not know God wholly. Consequently, it does know all that is in God actually. It is not necessary, however, that the intellect know the relation God has to all His effects, for this would mean that it knew God in so far as He is the ultimate meaning of all of them.

12. Although the knowledge of creatures does not belong to the substance of beatitude as something that beatifies, nevertheless, some knowledge of creatures pertains to beatitude as being in a way necessary for some act which the beatified person has to perform. For example, to know all who have been placed under his care belongs to the beatitude of an angel. Similarly, it belongs to the beatitude of the saints to know those persons who implore their help and even to know those other creatures from which they ought to rise to the praise of God.

Or it might be said that, even if the knowledge of creatures pertains in no way at all to beatitude, it does not follow that all knowledge of creatures is equally related to the beatific vision. For, when a cause is known, some effects are known immediately in it while others still remain rather hidden. For example, some conclusions can be drawn immediately from principles of demonstration while others cannot be except by means of numerous media; and one cannot come to know the latter by himself but must be led to them by someone else. The same is true of knowing the intelligible reasons of effects in their relation to the divine essence: some are hidden but others are manifest. Consequently, when one sees the divine essence he sees some effects but not others.

13. A thing can be in potency to something else in two ways. First, it can be in natural potency; and it is in this way that a created intellect is in potency to knowing all those things that can be manifested to it by its own natural light. A beatified angel is ignorant of none of these things, for were he ignorant of these his intellect would be imperfect. Secondly, a thing can be in merely obediential potency; and it is in this way that a thing is said to be in potency to those things above its nature which God can nevertheless cause in it. If such things are not reduced from potency to act, the potency is not imperfect. Consequently, the intellect of a beatified angel is not imperfect if it does not know all the things which God could reveal to it.

Or one could reply that if a potency is ordered to two perfections, and if the second is the final cause of the first, then that potency would not be imperfect if it should have the second without the first—for example, if one were to have health without the help of medicine which causes health. Now, all knowledge of created things is ordered to the knowledge of God. Consequently, granted the impossible position that a created intellect did not know creatures but still knew God, it would not be imperfect. Moreover, an intellect that sees God and knows more creatures is not more perfect because of this knowledge of creatures but rather by the fact that it knows God more perfectly. For this reason, Augustine says: "Unhappy the man who knows all things," that is, created things, "but does not know You. Happy is he who knows You, even if he does not know creatures. Moreover, if he knows You and creatures, he is not happier on account of them, but his happiness comes from You alone."

14. Change in thought, which is not had in beatified angels, can be understood in two different senses. First, thought is said to change as a result of reasoning from effects to causes or from causes to effects. Now, this discursive thinking is proper to reason and is beneath the clarity of angelic intellects. Second, change in thought can mean succession in the things that are thought about; and here we should note that there cannot be any succession in the knowledge by which angels know things in the Word, because they know many different things in one medium. But there is succession will respect to those things which they know through innate species or through the illuminations of higher angels. Hence, Augustine says: "God moves spiritual crea tures through time;" that is, they are changed in their affections.

15. The beatific vision is that by which God is seen through His essence and things are seen in God. There is no succession in this vision, nor do angels make any progress in it or in beatitude. But they can progress in their vision of things through innate species or through the illumination of superior angels; and this vision is measured, not by eternity, but by time—not by that time which is the measure of the first mobile thing’s motion, about which the Philosopher speaks, but by non-continuous time, such as that by which creation is measured. This is nothing other than the difference between "before" and "after" in the creation of things or in the succession of acts of under standing had by angels.

16. Christ’s body is finite and can be comprehended by physical sight. The divine essence, however, cannot be comprehended by spiritual sight, because it is infinite. Hence, no comparison can be made.

17. That argument would conclude if the intellect could know perfectly what is most knowable, namely, God Himself. Since this is not so, the argument does not hold.

i8. As is clear from what we have said, this difficulty from causes and effects can be answered in a similar way.

19. The intelligible representations of things are not in God the way in which colors are on a tablet or wall. This is clear from what we have said above. Hence, the argument proves nothing.

Answers to Contrary Difficulties:

We concede these arguments, since their conclusions are true even though they are not reached as they should be.


Parallel readings: Summa Theol., I, 12, 9; III Sentences 14, I, sols. 4-5.


It seems that it is, for

1. All cognition takes place through an assimilation of the knower to the known. Therefore, if an angelic intellect knows things in the Word, it should know them by means of likenesses existing within itself.

2. A spiritual thing is related to spiritual sight as a physical thing is related to physical sight. But a physical thing is known by physical sight only by means of an impression of the thing existing within it. The same is true, therefore, of spiritual sight.

3. The glory had in heaven does not destroy nature; instead, it perfects it. Now, the natural cognition of angels takes place through species. Therefore, their knowledge in glory, which consists in their vision in the Word, takes place through likenesses of things.

4. All knowledge takes place through some form. But the Word can not be the form of the intellect, except perhaps the exemplary form, since He cannot be the intrinsic form of anything. Consequently, an angelic intellect must know the things that it knows in the Word through other forms.

5. It is clear from the second Epistle to the Corinthians (12:4) that Paul in rapture saw the essence of God and there saw "secret words which it is not granted to man to utter." Now, he did not forget those words when he no longer saw the Word through His essence. Hence, he must have known them by means of some likenesses, which remained in his intellect. For the same reason, therefore, it seems that angels know through likenesses the things they know in the Word.

6. But it was said that when the Word departed from Paul, some traces of his vision remained in Paul’s soul, that is, some impressions or likenesses by which he could remember the things that he saw in the Word—just as impressions are left on the senses even after the objects that have been sensed are no longer present.—On the contrary, a thing leaves a greater impression on another when it is present than when it is absent. Therefore, if the Word when absent left an impression on Paul’s intellect, He also left an impression when He was present.

To the Contrary:

1'. Whatever is in God is God Himself. Consequently, when an angel sees God’s essence he does not see it by means of a likeness, nor does he see through a likeness the ideas of things as they exist in God.

2’. The natures of things are reflected in the Word like images in a mirror. Now, all the things reflected in a mirror are seen by means of their one likeness there. Hence, all the things known in the Word are seen through the form of the Word.

3’. An angelic intellect is like a painted tablet, for, as said in The Causes, "every intellect is filled will forms." Now, other pictures are not added to a tablet that is already painted; hence, it is proved in The Soul that the possible intellect can receive all things because it is "like a tablet on which nothing has been written." Consequently, an angel cannot have any likenesses of those things which he knows in the Word.



All cognition takes place through an assimilation of the knower to the known. Now, whenever one thing is made like a second thing in so far as the second thing is like a third, then the first thing is also like the third. For example, if a son is like his father in so far as the father is like the grandfather, then the son is like the grandfather. Now, one thing can be made like another in two ways: it can get this likeness immediately from the other, or it can get it by being assimilated to a third thing which is like the second. Cognition is had in two ways, also: we can know Socrates by seeing him either because our sense of sight is made like Socrates himself or because it is made hike a picture of Socrates. In either case, the assimilation is sufficient for us to know Socrates.

I say, therefore, that, when a thing is known by means of the hike ness of a second thing, that knowledge does not take place by means of some other likeness derived immediately from the thing known; and if the knower knows one and the same thing by means of its own likeness and also by means of its likeness to another thing, then these cognitions are different. This can be explained as follows.

Some knowing powers know only by receiving, not by forming something from what they have received. For example, the senses know merely those things whose species they receive and nothing more. Other powers, however, not only know what they receive, but can also form some other species from it. This is clearly the case of the imagination, which, having received the forms of gold and of mountain, forms a phantasm of a golden mountain. The same is true of the intellect, which, having comprehended the forms of genus and difference, forms the definition of a species. Consequently, when these powers know a thing through its likeness existing in another thing, it sometimes happens that a species other than that likeness is formed— a species which belongs immediately to the thing. For example, when I have seen a statue of Hercules, I can form another likeness which will belong immediately to Hercules; but this second act of knowing will be other than that by which I knew Hercules by his statue. If it were the same, then the same thing would happen in all other powers— which is manifestly absurd, because, when my external sense of sight sees Hercules in a statue, that knowledge does not take place through any other likeness than that of the statue.

Consequently, I say that the divine essence is itself a likeness of all things. Therefore, an angelic intellect can know things both through their likenesses and through the divine essence. But the act of knowledge by which it knows things through their likenesses is other than the act by which it knows things through the Word, even though those likenesses are caused by a conjunction of the angelic intellect to the Word cither through operations of the angelic intellect (similar to those of the imagination) or, as seems more probable, through an outpouring from the Word.

Answers to Difficulties:

1. Since the divine essence is a likeness of the things known through the Word, the angelic intellect’s union will the divine essence makes it sufficiently assimilated to these things to know them.

2. The Word can imprint something on an angelic intellect, but, as was said, the knowledge that would result from this impression would be other than that which is had through the Word.

3. Even though the glory had in heaven does not destroy nature, it elevates it to a level which it could not reach by itself, namely, that level where it can see things through God’s very essence without any likness acting as a medium in this vision.

4. The Word is not the intrinsic form of a thing in the sense that it is part of a thing’s essence. It is, however, a form within the intellect, since it is intelligible of its very nature.

5. When Paul no longer saw God’s essence, he remembered the things he had known in the Word by means of likenesses of things that still remained will him.

6. Those likenesses winch remained even when the Word had de parted were imprinted when Paul saw the Word through His essence. But, as is clear from what has been said above, when Paul saw through the Word, the vision itself did not take place through these impressions.


Parallel readings: Summa Theol., I, 56, 1; Contra Gentiles II, 98; III De anima, lectura 9, n. 721 seq., De causis, lectura 13 (P. 21:74


It seems not, for

1. As Dionysius says, angels do not know their own power. Now, if they knew themselves by means of their essence, they would know their power. Consequently, angels do not know their own essence.

2. If an angel knows himself, he knows himself, not through a like ness, but through his own essence; for, as is said in The Soul, "in those beings which exist without matter, the knower and the known are one and the same." But an angel cannot know himself by means of his own essence, since a thing is understood by means of a form within the intellect. Now, the essence of an angel cannot be the form of his own intellect, because the intellect itself inheres in his essence as its property or form. Consequently, an angel cannot know himself at all.

3. The same thing cannot be both active and passive, mover and moved, unless one of its parts is a mover or active and its other part is moved or passive. This is clear in the case of animals, as is shown in the Physics. But the knower and the known are related as active and passive. Consequently, it is impossible for an angel to know all of himself.

4. If an angel understands himself through his own essence, his essence must be the act of his intellect. But, unless it is pure act, no subsisting essence can be the act of anything else, for a material thing cannot be the form of another thing. Now, pure act of being belongs only to the divine essence. Consequently, an angel cannot know him self through his own essence.

5. A thing is understood only if it is stripped of matter and of the conditions of matter. But to be in potency is, in a way, a material condition which cannot be stripped from an angel. Consequently, an angel cannot understand himself.

6. If an angel understands himself through his own essence, his essence must be in his intellect. This, however, is impossible; for, as a matter of fact, his intellect is in his essence, and if one thing is in an other, this other cannot be in it. Consequently, an angel does not know himself by means of his own essence.

7. The intellect of an angel is mixed will potentiality. Now, nothing is reduced from potency to act by itself. Consequently, since an intellect is reduced to the act of knowing by the known, it will be impossible for an angel to understand himself.

8. Every potency has the perfection of its activity determined by the essence in which it is rooted. Consequently, an angelic intellect can understand because of the power of its essence. Now, the same thing cannot be a principle of acting and of being acted upon; and, since that which is understood is, in a way, acted upon, it seems that an angel cannot know his own essence.

9. Demonstration is an intellectual act. But a thing cannot be demonstrated by means of itself. Therefore, an angel cannot understand himself by means of his essence.

10. There is the same reason for holding that the will reflects upon itself as that the intellect does. But the will of an angel reflects upon itself only by means of its natural love, which is a kind of natural habit. Consequently, an angel can know himself only by means of some habit, and, therefore, he cannot know himself by means of his essence.

11. Operation lies as a medium between what is active and what is passive. But the knower and the known are related as active and passive. Now, since there is nothing intermediate between a thing and it self, it seems impossible that an angel could know himself.

To the Contrary:

1'. As Boethius says, what a lower power can do a higher power can. But our soul can know itself. Therefore, it is even more true that an angel can know himself.

2'. As Avicenna says, the reason why our intellect, but not our senses, knows itself is that the senses use a physical organ but the intellect does not. Now, an angelic intellect is even further removed from a physical organ than our intellect is. Therefore, an angel also knows himself.

3'. Since the intellect of an angel is godlike, it greatly resembles God’s intellect. But God knows Himself through His essence. There fore, an angel knows himself also through his essence.

4’. The more proportionate an intelligible is to an intellect, the more the intellect can know it. Now, there is no intelligible more proportionate to an angelic intellect than its own essence. Therefore, it knows its essence in a very high degree.

5’. In The Causes it is said: "Whoever knows intellectually knows his own essence, and returns to it in a complete reflection." There fore, angels can do this, for they know intellectually.



There are two types of action. One proceeds from the agent and goes out to an exterior thing, which it changes. An example of this type is illumination, which can properly be called an action. The second type of action does not go out to an exterior thing but remains in the agent as its perfection. Properly speaking, this is called operation. Shining is an example of this type.

Now, these two actions are at one in this, that both issue only from a thing which is actually existing and only in so far as it is in act. Consequently, a body does not shine unless it actually has light; and the same is true of its illuminating action.

The action of appetite, sense, and intellect is not, however, like the action that goes out to exterior matter; it is like the action that remains in the agent as its perfection. Consequently, in so far as he knows, a knower must be in act. It is not necessary, however, for the knower in knowing to become an efficient cause and for the known to become something passive; but inasmuch as one thing results from the knower and known, namely, an intellect in act, these two are but one principle of this act, which is understanding.

I say that one thing results from them inasmuch as what is under stood is joined to the understanding either through its essence or through a likeness. Hence, a knower is not related as active or as passive except for another consideration; that is, activity or passivity is required to some extent in order that the intelligible be united to the intellect. Efficient causality is required, because the active intellect

makes species actually intelligible; change is required because the possible intellect receives intelligible species, and the senses, sensible species. But understanding follows upon this change or efficient causality as an effect follows upon a cause. Consequently, just as a bright body shines when light actually exists in it, so also does the intellect under stand everything that is actually intelligible in it.

We must note, however, that there is no reason why a thing cannot be one thing actually and another potentially. For example, a trans parent body is actually a body, but it is colored only potentially. Similarly, it is possible for a thing to be in act in the order of existence but only in potency in the order of intelligibility. Now, in beings there are grades of act and potency. One being, prime matter, is in potency only. Another, God, exists only actually. All other intermediate beings exist both actually and potentially. Similarly, in the genus of intelligibles, one being, the divine essence, is in act only; another, the possible intellect, is only in potency, and for this reason the Commentator says that the possible intellect in the order of intelligibles is like prime matter in the order of sensibles. All the angelic substances lie in between; for they have something of potency and of act, not only in the genus of being, but also in the genus of intelligibility.

Now, prime matter cannot perform any action unless it is perfected by some form (and even then that action is a kind of emanation from the form rather than from the matter); because things that actually exist can perform actions only in so far as they are in act. Similarly, our possible intellect can understand nothing before it is brought into act by an intelligible form. Only then can it understand that thing to which this form belongs. Moreover, it can understand itself only by means of an intelligible form that actually exists in itself. But, since the essence of an angel, which is in act in the genus of intelligibility, is present to it, an angelic intellect can understand this intelligible reality within itself, namely, its own essence—and not through any likeness of it but through the essence itself.

Answers to Difficulties:

1. Angels know their power by comprehending it as it is in itself. They do not comprehend it, however, in so far as it has been modeled upon the eternal archetype, for this would involve comprehension of the archetype itself.

2. Even though in the order of existence an angel’s essence cannot stand in the relation of act to potency will respect to his intellect, in the order of understanding it is related to it as act is to potency.

3. The knower and the known are not related as active and passive but as one principle of activity, as is clear from what has been said above, even though they may seem to be so related from our manner of speaking.

4. Although an angel’s essence is not pure act, it nevertheless is will out matter. It is in potency merely in this respect, that it does not have its act of existence from itself. Consequently, there is no reason why it cannot be related to an angelic intellect as act in the order of under standing.

5. A thing that is understood need not be stripped entirely of matter; for it is evident that natural forms are never understood without matter, since matter is included in their definition. They must, how ever, be stripped of individual matter, that is, matter that lies under determinate dimensions. There is no reason, therefore, why angels need be separated from the kind of potency which they possess.

6. There is no reason why one thing cannot be in a second and the second in the first if this is in different ways, such as the ways in which a whole is in its parts and the parts are in the whole. The same is true here: the essence of the angel is in his intellect as an intelligible is in a knower, and his intellect is in his essence as a power is in a substance.

7. The intellect of an angel is not in potency will respect to his essence. In this respect, it is always in act. But will respect to other intelligible objects his intellect can be in potency. It does not follow, however, that when his intellect is in potency it is always reduced to act by some other agent. This is true only when it is in essential potency, as a person is before he learns something. When it is in accidental potency the potency a person is in who has habitual knowledge but is not using it—then it can go into act by itself, except that it might be said that his intellect is reduced to act by his will, which moves it to actual consideration.

8. As is evident from what we have said above, that which is under stood is not like something passive but like a principle of action. Consequently, the argument does not hold.

9. A thing can be the cause of knowing in two ways. First, it can be what is known. Thus, what is more known is the cause of cognizing what is less known; and in this way the medium of demonstration is a cause of understanding. Second, it can be the one who knows. Then the cause of knowledge is that which makes the intelligible to be present actually in the knower. Taken in this way, there is no reason why a thing cannot be known by means of itself.

10. Natural love is not a habit but an act.

11. The act of understanding is not a medium that stands as a reality between the knower and the known; it proceeds from the union of both.


Parallel readings: Summa Theol., I, 56, 2 107, I; Contra Gentiles II, 98; Il Sentences II, 2, 3; In I Cor., c. 1 lectura i (P. 1

Difficulties (First Series):

It seems not, for

1. As Dionysius says, even the angels themselves do not know their mutual relationships. Now, if one angel knew another, angels would know these. Consequently, one angel does not know another.

2. As is said in The Causes: "An intelligence knows what is above it in so far as that is its cause, and it knows what is below it in so far as that is its effect." But our faith does not teach that one angel is the cause of another. Consequently, one angel does not know another.

3. As Boethius says: "The universal is had in intellection, the singular in sensation." Now, since an angel is a person, he is, in a way, a singular. Consequently, it seems that one angel does not know another angel, because he knows merely through intellection.

Difficulties (Second Series):

1. It seems that an angel does not know another angel by means of the latter’s essence, because that by which the intellect understands must be within the intellect. But the essence of one angel cannot come into the intellect of another; only God can be substantially present in the mind of an angel. Consequently, an angel cannot know another angel by means of the latter’s essence.

2. It is possible for one angel to be known by all angels. Now, that by which a thing is known is joined to the one who knows. So if one angel were to know another angel by means of the latter’s essence, then the angel known could be in many places, because the angels who could know him might be in many places.

3. The essence of an angel is a substance; his intellect, being a power, is an accident. Now, a substance is not the form of an accident. Consequently, the essence of one angel cannot be for the intellect of an other angel the form by which he knows.

4. A thing cannot be known to the intellect by its presence if it is separated from it. But the essence of one angel is separated from the intellect of another. Consequently, one angel is not known by another through the presence of his essence.

Difficulties (Third Series):

1. It seems that one angel cannot know another by knowing through his own essence, because the lower angels lie. below the higher, as sentient creatures also do. Consequently, if a higher angel could know other angels by knowing his own essence, he could also know all sentient things in the same way, and not, as is said in The Causes, by means of forms.

2. One thing leads to the knowledge of another only in so far as it resembles that other. But the essence of one angel is only in generic agreement will that of another angel. Consequently, if one angel were to know another merely by knowing his own essence, then he would know that other only generically, and this would be imperfect knowledge.

3. That through which a thing is known is an intelligible representation of it. Now, if one angel knew all others by means of his own essence, then his own essence would be an intelligible representation of what is proper to all angels. But this property seems to belong to the divine essence alone.

Difficulties (Fourth Series):

1. It seems that one angel does not know another by means of a like ness or species existing within himself, because, as Dionysius says, angels are lofty intelligible lights. Now, a light is not known by means of a species, but only by means of itself. Therefore, an angel cannot be known by means of a species.

2. Every creature is a shadow. This is evident from Origen’s commentary on that verse in the Gospel of St. John (1:5): "And the dark ness [shadows] did not comprehend it." Now, a likeness of a shadow must itself be a shadow; a shadow, however, is not a principle that manifests but one that conceals. Hence, since an angel is a creature and is therefore a shadow, he cannot be known by means of a likeness. If he is known, he must be known by means of a God-given light existing within him.

3. An angel is closer to God than the rational soul is. Now, according to Augustine, the soul knows all things and judges about all things, not by means of any arts which the soul may have brought will it to the body, but by means of the connection it has will the eternal intelligible representations. Much more so, then, will one angel know another, not indeed by means of a likeness, but by means of an eternal intelligible representation.

Difficulties (Fifth Series):

1. It seems that one angel cannot know another even through an innate likeness. For an innate likeness is similarly related to what is present and to what is absent. Consequently, were one angel to know another by means of an innate likeness, he would not know when that angel was present and when he was absent.

2. God could make another angel. But an angel would not have within him the form of an angel that does not yet exist. Consequently, if, by his natural cognition, an angel knows other angels only by of innate forms, the angels that exist now would not know by natural cognition an angel that would come into existence later.

Difficulties (Sixth Series):

1. It seems that one angel cannot know another through forms impressed by immaterial beings, as the sense knows through forms received from sensible things, because, if this were true, then the lower angels would not be known by the higher, since higher angels do not receive any influence from the lower.

Difficulties (Seventh Series):

1. It seems that one angel cannot know another even through abstracted forms, such as the agent intellect abstracts from phantasms, because then the lower angels would not know the higher.

From all this it seems that one angel does not know another.

To the Contrary (First Series):

1'. In The Causes we read: "Every intelligence knows the things that do not undergo corruption and are not measured by time." Now, angels are incorruptible and outside of time. Consequently, one angel is known by another.

2’. Likeness is a cause of knowledge. But one angel has more in common will the intellect of another than material things have. Consequently, since angels know material things, it is even truer to say they know other angels.

3'. The essence of one angel is more proportionate to the intellect of another than the divine essence is. But, since angels see God through His essence, it is even truer to say that they can know the essences of other angels.

4’. As is said in The Intelligences: "Any substance that is immaterial and free from composition can know all things"; and this is proved in The Soul, where it is shown that the intellect is free from composition "and so can know all things." Now, to be free from matter and composition belongs especially to angels. Consequently, they know all things, and one knows another.

To the Contrary (Second Series):

1'. It seems that one angel can know another by means of the latter’s essence. For Augustine says that angels show what they have seen "by one spirit mingling will another." But such a mingling is possible only if one spirit can be joined to another by means of his essence. Consequently, one angel can be joined to another by means of his essence, and thus, through his essence, be known by that other.

2’. Knowledge is an act. Now, contact is sufficient for action. Since there can be spiritual contact between one angel and another, one angel can know another by means of the latter’s essence.

3’. The intellect of one angel has more in common will the essence of another angel than will the likeness of a material thing. But the intellect of an angel can be informed by the likeness of a material thing so that it knows it. Consequently, the essence of one angel can be the form whereby the intellect of another can know him.

4’. According to Augustine, intellectual vision is had of those things whose likenesses are the same as their essences. Now, one angel knows another only by means of intellectual vision. Consequently, he does not know that angel by means of a likeness other than that angel’s essence. Hence, the same must be said as was said previously.

De veritate EN 72