Question Two of Chapter Seven of the Third Decade
Whether demons know the thoughts of human beings
It is asked whether demons know the thoughts of human beings.
To this it first appears that one must respond affirmatively. For, as Gregory says in the Moralia, the intellects of the blessed when they rise again, directing themselves simultaneously into the intellect of each of the other blessed, will penetrate their consciences.
But those who rise again will be like the angels, Matthew 22. Therefore good and evil angels can do this in like manner.
In response it must be said that a human being’s thought can be known in two ways.
In one way, indirectly—that is, in its effect. In this way not only human beings and good angels, but demons also can know the thoughts of hearts; and good angels and demons know them the more subtly, the more hidden the effects of this kind are.
A thought is sometimes known not only through some exterior act or effect, such as speech or operation, but also through certain signs of the face and a change of countenance, or through certain signs of the body, which is moved in diverse ways according to the diversity of affections.
For Ecclesiasticus 13 says: “The heart of a human being changes his face.”
And Juvenal says in Book III: “You may detect the torments of the mind lying hidden in the face of the sick.”
And Ovid says in The Art of Love: “Often the silent countenance has voice and words.”
In this way human beings too know the thoughts of hearts, but good and evil angels do so the more easily, the more subtly they discern hidden corporeal alterations.
Physicians too know certain affections through the pulse—for example, that a human being is sorrowful or is in love.
Master Bonaventure calls this cognition conjectural. According to this indirect or conjectural cognition, or cognition in the effect, one must understand Augustine’s statement in Book XXII On the Literal Meaning of Genesis that angels know our thoughts even against our will.
Likewise, in the book On the Divination of Demons, he says: “Demons learn with complete facility the dispositions of human beings, not only those uttered by voice but also those conceived in thought, when certain signs are expressed in the body from the mind.” Thus he.
In the other way, thoughts can be known directly, insofar as they exist in the will. Concerning this the second conclusion is that neither demons, nor angels, nor human beings know thoughts, but God alone.
This is proved first thus. Angels and demons naturally know from impressed and innate species. The human will, however, agrees with no thing from which its likeness can be elicited. Therefore neither wills, nor the affections of wills, nor thoughts insofar as they exist in the intellect can be known directly by a human being or by good or evil angels, but only by God, to whom alone the human will is subject and who alone can operate in it, since he is its principal object and ultimate end.
For this reason it is said in Jeremiah 17: “The heart of man is perverse and inscrutable; who shall know it? I, the Lord, who search the heart and prove the reins.”
And 1 Corinthians 2 says: “For who among human beings knows the things of a human being except the spirit of the human being which is in him?”
Ambrose expounds these words thus: “Who among human beings knows the wills and secrets of the heart except the spirit of the human being which is in him?”—that is, except that person’s own mind and not another’s. For it is manifest that our thoughts are known by no one except our own mind, which he here calls the spirit.
“So too, the things which are of God”—that is, the secrets and hidden things of God—“no one can know except the Spirit of God which is in him.” This is an argument from the lesser.
And Augustine says in the book On Ecclesiastical Dogmas: “It is certain that the devil does not see our interior thoughts.”
What Master Bonaventure says also supports this. Just as God gave to the will of a rational creature dominion or choice, over which no power presides except the divine power, so to its cognitive power he gave the secret of conscience, whose secrets and depths no one penetrates except divine wisdom.
Therefore no creature, whether human or angelic, can know the secrets of a human conscience except through signs, through conjectures, through a revelation of God, or through the disclosure and declaration of the human being.
These things are from Thomas in the questions On Truth and in the First Part, question 57; from Master Bonaventure; and from Master Johannes de Turrecremata upon chapter Quodam loco, cause 25, question 3.
Master Hervaeus, however, together with Master Johannes Scotus, says that demons know our thoughts with respect to the subject, the object, and the affection toward which they incline, but not with respect to the end.
For example, they know what we are thinking, but they do not know toward what end. They know that you are thinking about a woman, but they do not know whether it is toward pleasure or toward another end.
To Gregory’s argument it must be said that in the resurrection, on account of the brightness and subtlety of their bodies, their minds will be penetrated with respect to the quantity of grace and glory, but not with respect to the thoughts of their hearts.
The same is said of good and evil angels from now until the day of judgment.
These things are from the authorities adduced above.