Thomas Aquinas, Disputed Questions on Truth (De Veritate)

2. As the body receives its shape from its figure, so does the intellect receive its shape from the species of that which it actually thinks about. Now, when the eye sees a body, it simultaneously sees the body's shape. Therefore, when an angel sees another angel's intellect, he sees its thought.

3. Since the species in an intellect are actually intelligible, they are more intelligible than the forms existing in material things, which are merely potentially intelligible. Now, angels understand the forms of material things by means of forms which they have within themselves. Consequently, it is even truer that they understand the forms within our intellect; hence, they know our thoughts.

4. Man never knows without a phantasm. But angels know the phantasms in our imagination. Consequently, Augustine says: "The spiritual likenesses of material things existing within our soul are known to spirits, even to unclean spirits." Therefore, angels know our thoughts.

5. By means of the forms he has within himself an angel can know whatever he can do by these forms. Now, an angel can make an impression on our intellect by enlightening and cleansing us. Therefore, it is even truer that he can know our thoughts.

6. Augustine says: "Demons sometimes learn men's dispositions with the greatest ease, not only when they are expressed by speech, but even when conceived in thought and expressed by the soul through certain signs in the body." Now, there is no thought that does not leave a trace on the body. Consequently, the demons know all our thoughts, and much more so do the angels.

7. Commenting on that verse in the Epistle to the Romans (2:15), ". . . their thoughts between themselves accusing or also defending one another," Origen says that this passage should be understood as referring to thoughts which, during their existence, left marks on those who had them. Consequently, every thought leaves some mark on the soul. Now, this mark cannot be unknown to an angel, because he sees the whole soul. Hence, angels know our thoughts.

8. Angels know effects in their causes. Now, as Augustine says, knowledge proceeds from the mind, and actual understanding proceeds from habitual knowledge. Consequently, since angels know our mind, they know what we know and what we are actually thinking.

To the Contrary:

1'. We read the following in Jeremias (17:9-10): "The heart is perverse . . . and unsearchable. Who can know it? I . . . the Lord . . . ." Therefore, it belongs to God alone to know the heart's secrets.

2'. The following is found in the Psalms (7:10): "The searcher of hearts and reins is God." It seems, therefore, that God alone can search our hearts.

REPLY:

Of themselves angels cannot see the thoughts of the heart directly; for, in order that the mind actually think something, the will must make an intention moving the mind to act with respect to its mental species. This is clear from what Augustine has said. Now, an angel cannot naturally know the motion in the will of another person, because he naturally knows by means of forms that have been given him, and these are likenesses of things existing in nature. The motion of the will, however, has no dependence on or connection with any natural cause. It is the divine cause alone that can influence the will. Consequently, the will's motion and the heart's thoughts can be known, not by any likenesses of natural things, but only in the divine essence, which leaves its imprint on the will. Thus, angels cannot know the thoughts of the heart directly, but only if they are revealed to them in the Word.

Sometimes, however, an angel can indirectly come to know the heart's thoughts, and this can happen in two ways. First, it happens inasmuch as a motion in the body results from an actual thought, as when one is affected by joy or sadness from what he thinks, and his heart is moved in some way or other. By this means, even doctors can sometimes know what a heart is experiencing. Second, an angel can know thoughts in so far as a person gains or loses merit from what he is actually thinking; for thus the doer's or thinker's condition is somehow changed for good or for evil, and angels can know this change in his condition. But this gives only a general knowledge of what was thought, because, as a result of many different thoughts, a person can merit or demerit, be joyful or sorrowful, in the same way.

Answers to Difficulties:

1. That cleansing of which Dionysius speaks should be understood as being from ignorance, not from the impurity of sin.

2. From one species which the intellect has within itself, many distinct thoughts arise--just as we can think many different things about man from the one species we have of man. Consequently, even if an angel sees our intellect shaped to the species of man, it does not follow that he knows determinately what the heart is thinking about.

3. We do not actually think of all the things whose species we have within us, because sometimes species are in us only in the state of habit. Consequently, from the fact that the species in our intellects are seen by angels it does not follow that they know our thoughts.

4. By means of the same phantasms, our reason can direct its thought to different objects. Consequently, even should one know the phantasms by which the soul thinks, it would not follow that he knew the thoughts themselves. Thus, Augustine says: "If demons could see clearly a man's internal thought, arising from his virtues, they would not tempt him."

5. As a consequence of an angel's action, we may be made capable of thinking certain things; but in order to think something actually, we must make an act of the will, and this by no means depends upon an angel. Consequently, even though angels can know our intellect's power, that is, the power by which we can speculate about intelligible things, it does not follow that they know our actual thoughts.

6. Bodily motion, found in the passions of the soul, does not follow all knowledge but only practical knowledge. For, as is said in The Soul, when we consider something speculatively, we are related to the things we are considering "as though we were looking at them in pictures." Moreover, even when bodily motion does take place, it indicates thought only in a general way, as we have said.*

7. Those marks are nothing other than merits or demerits; and from these, thoughts can be known only in a general way.

8. Even though angels know our mind and our habitual knowledge, it does not follow that they know what we are actually thinking, because many actual thoughts can arise from one thing known habitually.