Chapter Seven of the Third Decade
On the power and condition of the demons themselves, concerning which four little questions will be elucidated
Question One of Chapter Seven of the Third Decade
Whether demons know future things
It is asked whether demons know future things.
To this it is answered that there is a threefold genus of future things.
Certain future things have a determinate and infallible cause, as do those which concern the motion of the superior bodies, in which there is determination and the removal of every impediment.
Concerning such things the first conclusion is that demons know future things of this kind in their causes. Such are the things which occur concerning the motion of the heaven, as risings, settings, eclipses, and conjunctions of the luminaries. They know all these things much better through the innate species of their causes than astronomers know them through art.
The second genus of future things consists of those which have a determinate cause, but one which is nevertheless sometimes fallible, as are those things which occur according to inferior nature.
Such a thing has a determinate cause because the intention of nature moves determinately toward one thing. It is nevertheless fallible because a manifold impediment can occur. For example, a sown field, if the soil is fertile and the disposition of the superior bodies is good, will bring forth abundant fruit.
Concerning such things the second conclusion is that demons know future things not with complete certainty but by conjectural cognition.
In this way an astrologer predicts certain future things which follow in these inferior things from the motions of the heaven, but which can nevertheless be impeded because of a defect in the inferior causes.
Cognition of such things approaches certainty to the degree that more causes concurring toward one effect are known, and to the degree that the power of the cause is known better. Hence, because demons are most subtle, they know such things better.
The third genus of future things consists of those which have an indeterminate and fallible cause, as are those things said to be open to either alternative. Such are the things which depend upon our will, which is indeterminate because it can move toward opposites, and is also fallible because many things can occur even to someone willing to accomplish something.
Concerning such things the third conclusion is that demons do not know them, but God alone does.
Demons can divine and foretell future things of the first kind with certainty; those of the second kind, not with certainty; those of the third kind, in no way. God alone knows these, together with anyone to whom God wills to reveal them. From the usurpation of his act, those who devote themselves to foretelling future things are called diviners.
The fourth conclusion, as a corollary, is that although demons know future things in the first way, faith is nevertheless not to be placed in them when they reveal them, because their intention is to deceive. If they sometimes say true things, they do this so that they may accustom human beings to believe them in other matters.
Faith is therefore not to be placed in their divinations.
These things are from Thomas, Bonaventure, and Master Johannes the Cardinal upon chapter Sciendum, cause 26, question 3.
But if it is asked how demons sometimes know present things, revealing what kings are doing now, and so forth, it is answered that demons are not moved locally in order to acquire some cognition, although they are indeed moved in order to operate something in a place.
Therefore, just as a demon does not need motion in order to know, neither does he require a delay of time for local motion. He can therefore immediately be present by applying himself and can reveal the matter, just as our soul also passes instantly in thought from Gaul to Syria.
These things are from Thomas, First Part, question 113.