Some things, not all. They cannot reveal all things, because they do not know all things. This is the common opinion of the orthodox after Tertullian and Origen: namely, of Augustine, Eusebius, Anselm, Rabanus, Damascene, and St. Thomas. I shall set down only the words of Mark the historian, who, after narrating the mendacious answers of the idol of Venus, subjoins these things:
Demons are such that, in order to deceive, they say nothing true. Nor can they certainly foreknow anything, but from things likely to be true they present themselves among those who serve them as though they knew things beforehand. For how can those who have fallen away from the truth speak truth? If in some things it happens that they divine, this happens from what occurs, in the same way as it happens also among human beings, who often predict certain future things about a matter about to happen.
These words, spoken rather obscurely, are to be understood thus, so that they are true: demons prefer to lie, but can speak truth if they wish, and even customarily do speak it sometimes, yet in such a way that they deceive by this very truth. They can also predict scientifically some things which do not surpass created knowledge, according to the things that must soon be said.
[margin: Demonic knowledge: Tertullian, Apologeticus, chapter 21; Origen; Eusebius, Preparation for the Gospel; Augustine, On the Divination of Demons; John Damascene, On the Orthodox Faith, book 2, chapter 4; Anselm, On the Fall of the Devil, chapter 21; Rabanus on chapter Sciendum, 26 question 4; Thomas Aquinas on demons and in part 1, question 56; Mark the Historian, Life of St. Porphyrius of Gaza, on lying demonic responses]
First, the demon cannot certainly predict those things which are altogether freely future. Such are, first, those which depend absolutely on the will of God: supernatural mysteries, and also the governments and changes of kingdoms and commonwealths, because the hearts of princes are in the hand of God, who alone changes them as he pleases. Second are those things which depend on the freedom of human choice, such as what I am going to do or think tomorrow. Third are future contingents in the strict and proper sense, as long as they do not have a certain and determined cause.
Second, from those things which he does not certainly know, the demon can predict many things only probably and by making conjecture. For by long observation he has acquired for himself the highest experience, he is strong with angelic acuteness of intellect, and he knows very well the powers of natural things and to what they can incline the human will through the sensitive appetite. He knows the temperaments and affections of all human beings; he knows what usually follows from these and those things. Hence it happens that he often predicts exactly what and when people are going to do something, or even that God is going to punish this or that people, that such an army will be afflicted by sword, famine, or pestilence, or that such a person will be killed by such a person. For he can gather this also from the diligence and trustworthiness of conspirators, and from the sluggishness and carelessness of guarding or repelling danger.
Thus, in Nicetas, that fanatic Basilacius predicted to Isaac the blinding and deposition from the throne which soon followed. This seer was living near Rhaedestus and was considered a prophet by the common people. But Nicetas says:
He was saying nothing true or clear about future things, but poured forth confused words, self-contradictory and perplexed. Although he sometimes mixed in certain ridiculous things, he nevertheless drew a crowd of shepherds, farmers, and oarsmen. By touching the breasts of women who came to him, and by exploring such things, he produced obscure oracles; and to most questions he did not respond. He carried out his divinations with running about and mad gestures. There also stood by him a certain little old woman, stupid and insane, related to him, who explained to those consulting him what the gestures of Basilacius were signifying concerning future things and interpreted his silence as wise speech. Thus, as I said, the man was commonly held to be a seer and was thought to predict future things, especially by little women, to whom filthy questions and shameful entanglements of garments were dear as sport and play. To sensible people he seemed an inept stage-player and an old blockhead. There were also those who not obscurely indicated that he was endowed with a Pythonic spirit; and I strongly agree with their judgments.
Quite rightly so: the obscene inquiry, running about, and perplexed words all prove that he was a Satanic fanatic. So too do the things which follow:
When the emperor came to him, he neither received him as one endowed with such great power, nor responded to his greeting, “Hail, father Basilacius,” nor thanked him by a silent nod of the head. But running this way and that, like a little foal or a raging man, he cursed those who came near, not even sparing the emperor himself. At last, after omitting those restless agitations, with the staff which he carried in his hands he erased the eyes of the emperor’s image, which had been painted on the wall of his chamber. He even tried to remove the felt cap from its head. When he had done this, the emperor despised him as a madman and went away.
The event soon proved the prophecy; yet any person of keen prudence could have foreseen it, since Alexius was tending most diligently toward his brother’s destruction, while Isaac, with inopportune security, was shutting out and repelling all informers, so that he seemed to wish to perish.
[margin: Nicetas Choniates, book 3, on Basilacius and the probable prediction of Isaac’s blinding]
Third, the Devil can certainly predict whatever depends on necessary causes, that is, those which cannot be impeded by other natural causes, such as the motions of the heavens, eclipses, conjunctions of stars, and things of that sort. But those things which do not happen necessarily, but only for the most part, because they can be impeded by other natural causes, such as showers, rains, storm-clouds, sounding tempests, and other things of this kind, he knows by conjectures and predicts only probably. He can also certainly predict those things which he knows that he himself, if God permits, is going to do. For example, if, God permitting, he himself was the author and bearer of some pestilence, he knows that the violence of the plague is going to cease on a certain day; and still more certainly if, by pact, the disease will cease when some certain sign hidden somewhere or agreed upon is removed. He will be able to predict the end of the evil with certainty.
I think this was the case with that man of Famagusta in Cyprus, who, after gathering an assembly of the people in the forum, predicted that he would die within the space of an hour and that, as soon as he was dead, the plague would cease. Both things happened. A demon had manifested this to him, as Villamontius relates. Likewise the demon can predict those things which he has understood by revelation, whether that revelation is contained in Sacred Scripture or was otherwise manifested to the demon by God. By this path malignant spirits once predicted many things about the mysteries of the faith, the birth of Christ and his miracles, the overthrow of idolatry, and similar things. In this way they taught Hermes that the superstition of the Egyptians would be abolished; Apollo announced that he yielded to the Hebrew boy; and other things of this kind have been carefully gathered by Steuchus Eugubinus.
[margin: Villamontius, Peregrinationes, book 2, chapter 7, on the Famagusta plague-prediction; Augustine, City of God, book 8, chapter 23, and Steuchus Eugubinus, Perennial Philosophy, book 14, on Hermes and Apollo]
Fourth, one must not at all doubt that the demon retains in memory all past things which he has received either by someone else’s report or which were done in his own presence. For then the act of cognition, knowing the thing as present, left its species impressed in the demon’s mind.
Fifth, there is no obscure question about present things. Whatever things have been produced by an external act, such as secret thefts, lost things, treasures formerly buried, and metals underground, which escape human cognition, are known to demons. Concerning thoughts alone, remaining in the mind, it is disputed whether the demon knows them. Experience has often proved him not to be a lying accuser, but one who, through energumens, strikes with true darts of infamy. I know what Scotus, Durandus, and Ockham thought. Yet I prefer the more common opinion of Albert the Great, Alexander of Hales, St. Thomas, Bonaventure, Richard, and Ariminensis: by his natural power he cannot know any free affections or spontaneous thoughts of a human being without some manifestation. This is proper to God. By this argument the holy Fathers Ambrose and others prove the divinity of Christ and the Holy Spirit from cognition of the secrets of thoughts.
Even Gentiles confessed that such thoughts are known only to the divine nature and that other beings do not know them. But if thoughts are disclosed by a motion of the face or of some member, or by some other external sign, demons perceive the inward affections of the soul more skillfully and more cleverly from such indications than the most practiced physicians do, as Augustine and Cassian teach. The ancient cheat can also disturb a human being so violently by phantasms sent in that the person can scarcely turn his mind to anything else, or think anything else at that time, than what has been suggested by him. Thus it happens that he seems to divine the things a person is thinking. This happened in the Albigensian vision of which Cardan writes from Augustine. Thus too Scotus of Parma, at Maastricht in the year 1579, used to hunt for this knowledge of thoughts. He would say, “Think whatever you wish, and I shall divine the thought.” Obviously the demon would immediately send in a very troublesome thought about some matter known to the mage. In the year 1600, that Greek little impostor among the Brabanters did the same thing. By this fraud Apollonius of Tyana was famous in Philostratus.
[margin: Knowledge of thoughts: 3 Kings 8:39 and Acts 1:24; Ambrose on Luke 5, Jerome on Matthew 9, Chrysostom, homily 30 on Matthew, Cyril, book 2 on John, Augustine, and Didymus, On the Holy Spirit, on divine knowledge of hearts; Xenophon, book 4 on Socrates; Apollonius of Tyana’s oration to Domitian; Julian in Ammianus, book 25; Gellius; Augustine, On the Divination of Demons, chapter 5; Cassian, Conference 7, chapter 16; Gerson on examining doctrines, letter O near the end, on demonic inference from bodily signs and imagination]
Sixth, some frauds of the Devil should be noted concerning these things. When he is ignorant of a future matter, then, if he deals before the more prudent and learned, he answers in a weak tone, ambiguously, or in a perplexed and obscure way, so that he is scarcely understood. Various ancient writers supply examples, and Grillandus gives a more recent one, also testifying that the same is customarily done by him. But if he deals with the ignorant and simple, who will not easily detect the deception, he lies boldly and openly.
The reason for answering so ambiguously is that, however the matter turns out, he may obtain praise if it happens according to the consultant’s wish; but if it happens otherwise, he can pretend that the person asking was ignorant and dull, and did not understand the meaning of the answer. Behold, he answers Croesus:
Croesus, after crossing the Halys, will destroy great kingdoms.
If Croesus had conquered Cyrus, the demon would have said, “This is what I meant: that you would lay waste all the enemy’s forces.” When Croesus is conquered, he says, “This is what I meant: that you would lose your very great kingdoms. Why did you not grasp my meaning?” The mother of Ferratus, count of Flanders, received a similar answer when the son, after an unhappy battle, exchanged a crown for a prison. Read Gaguin, book 7 of the History of France, and Bernard Girard, book 10 of the Annals.
[margin: Grillandus on ambiguous demonic answers; Croesus; Gaguin, History of the Franks, book 7, and Bernard Girard, Annals, book 10, on Ferratus, count of Flanders]
Seventh, one must know that by the speed with which demons are strong, they can very quickly announce things done in remote regions at long distances on the road, so that things predicted long before by the ignorant may be thought to have been spoken beforehand. Thus Apollonius, when he was at Ephesus, exclaimed that Domitian was being killed at Rome, as if he were present at the spectacle. Gellius reports another example about a certain young man, Aimonius another about Charibert, Grillandus another from his own time, and Nicholas Remigius many from our age. Whoever wishes more should read Grillandus, Michael Medina, and Binsfeld.
[margin: Philostratus, life of Apollonius, book 8; Gellius, Attic Nights, book 15, chapter 18; Aimoinus, Annals, book 3, chapter 22; Grillandus, question 6, number 8, and number 3; Nicholas Remigius; Michael Medina, On Right Faith in God, book 2, chapter 1; Binsfeld, under C. de maleficiis, note 10, on rapid demonic reporting]