Whatever system we may follow on the nature of angels, or demons, or souls separated from the body; whether we consider them as purely spiritual substances, as the Christian church at this day holds; whether we give them an aërial body, subtile, and invisible, as many have taught; it appears almost as difficult to render palpable, perceptible, and thick a subtile and aërial body, as it is to condense the air, and make it seem like a solid and perceptible body; as, when the angels appeared to Abraham and Lot, the angel Raphael to Tobias, whom he conducted into Mesopotamia; or when the demon appeared to Jesus Christ, and led him to a high mountain, and on the pinnacle of the Temple at Jerusalem; or when Moses appeared with Elias on Mount Tabor: for those apparitions are certain from Scripture.
If you will say that these apparitions were seen only in the imagination and mind of those who saw, or believed they saw angels, demons, or souls separated from the body, as it happens every day in our sleep, and sometimes when awake, if we are strongly occupied with certain objects, or struck with certain things which we desire ardently or fear exceedingly—as when Ajax, thinking he saw Ulysses and Agamemnon, or Menelaüs, threw himself upon some animals, which he killed, thinking he was killing those two men his enemies, and whom he was dying with the desire to wreak his vengeance upon—on this supposition, the apparition will not be less difficult to explain. There was neither prepossession nor disturbed imagination, nor any preceding emotion, which led Abraham to figure to himself that he saw three persons, to whom he gave hospitality, to whom he spoke, who promised him the birth of a son, of which he was scarcely thinking at that time. The three apostles who saw Moses conversing with Jesus Christ on Mount Tabor were not prepared for that appearance; there was no emotion of fear, love, revenge, ambition, or any other passion which struck their imagination, to dispose them to see Moses; as neither was there in Abraham, when he perceived the three angels who appeared to him.
Often in our sleep we see, or we believe we see, what has struck our attention very much when awake; sometimes we represent to ourselves in sleep things of which we have never thought, which even are repugnant to us, and which present themselves to our mind in spite of ourselves. None bethink themselves of seeking the causes of these kinds of representations; they are attributed to chance, or to some disposition of the humors of the blood or of the brain, or even of the way in which the body is placed in bed; but nothing like that is applicable to the apparitions of angels, demons, or spirits, when these apparitions are accompanied and followed by converse, predictions and real effects preceded and predicted by those which appear.
If we have recourse to a pretended fascination of the eyes or the other senses, which sometimes make us believe that we see and hear what we do not, or that we neither see nor hear what is passing before our eyes, or which strikes our ears; as when the soldiers sent to arrest Elisha spoke to him and saw him before they recognized him, or when the inhabitants of Sodom could not discover Lot's door, although it was before their eyes, or when the disciples of Emmaus knew not that it was Jesus Christ who accompanied them and expounded the Scriptures; they opened their eyes and knew him only by the breaking of bread.
That fascination of the senses which makes us believe that we see what we do not see, or that suspension of the exercise and natural functions of our senses which prevents us from seeing and recognizing what is passing before our eyes, is all of it hardly less miraculous than to condense the air, or rarefy it, or give solidity and consistence to what is purely spiritual and disengaged from matter.
From all this, it follows that no apparition can take place without a sort of miracle, and without a concurrence, both extraordinary and supernatural, of the power of God who commands, or causes, or permits an angel, or a demon, or a disembodied soul to appear, act, speak, walk, and perform other functions which belong only to an organized body.
I shall be told that it is useless to recur to the miraculous and the supernatural, if we have acknowledged in spiritual substances a natural power of showing themselves, whether by condensing the air, or by producing a massive and palpable body, or in raising up some dead body, to which these spirits give life and motion for a certain time.
I own it all; but I dare maintain that that is not possible either to angel or demon, nor to any spiritual substance whatsoever. The soul can produce in herself thoughts, will, and wishes; she can give her impulsion to the movements of her body, and repress its sallies and agitations; but how does she do that? Philosophy can hardly explain it, but by saying that by virtue of the union between herself and the body, God, by an effect of his wisdom, has given her power to act upon the humors, its organs, and impress them with certain movements; but there is reason to believe that the soul performs all that only as an occasional cause, and that it is God as the first, necessary, immediate, and essential cause, which produces all the movements of the body that are made in a natural way.
Neither angel nor demon has more privilege in this respect over matter than the soul of man has over its own body. They can neither modify matter, change it, nor impress it with action and motion, save by the power of God, and with his concurrence both necessary and immediate; our knowledge does not permit us to judge otherwise; there is no physical proportion between the spirit and the body; those two substances cannot act mutually and immediately one upon the other; they can act only occasionally, by determining the first cause, in virtue of the laws which wisdom has judged it proper to prescribe to herself for the reciprocal action of the creatures upon each other, to give them being, to preserve it, and perpetuate movement in the mass of matter which composes the universe, in himself giving life to spiritual substances, and permitting them with his concurrence, as the First Cause, to act, the body on the soul, and the soul on the body, one on the other, as secondary causes.
Porphyry, when consulted by Anebo, an Egyptian priest, if those who foretell the future and perform prodigies have more powerful souls, or whether they receive power from some strange spirit, replies that, according to appearance, all these things are done by means of certain evil spirits that are naturally knavish, and take all sorts of shapes, and do everything that one sees happen, whether good or evil; but that in the end they never lead men to what is truly good.