If those forms were their own, and we suppose with several ancient and some new writers that angels, demons, and even human souls have a kind of subtile, transparent, and aerial body, the difficulty lies in knowing how they can condense the transparent body, and render it visible when it was before invisible; for if it was always and naturally evident to the senses and visible, there would be another kind of continual miracle to render it invisible, and hide it from our sight; and if of its nature it is invisible, what might can render it visible? On whatever side we regard this object it seems equally miraculous, whether to make evident to the senses that which is purely spiritual, or to render invisible that which in its nature is palpable and corporeal. The ancient fathers of the church, who gave to angels subtile bodies of an airy nature, explained, according to their principles, more easily the predictions made by the demons, and the wonderful operations which they cause in the air, in the elements, in our bodies, and which are far beyond what the cleverest and the most learned men can know, predict, and perform. They likewise conceived more easily that evil angels can cause maladies, render the air impure and contagious, that they inspire the wicked with wrong thoughts and unjust desires, that they can penetrate our thoughts and wishes, that they foresee tempests and changes in the air, and derangements in the seasons; all that can be explained with much more facility on the hypothesis that demons have bodies composed of very fine and subtile air. St. Augustine[440] had written that they could also discover what is passing in our mind, and at the bottom of our heart, not only by our words, but also by certain signs and movements, which escape from the most circumspect; but reflecting on what he had advanced in this passage, he retracted, and owned that he had spoken too affirmatively upon a subject but little known, and that the manner in which the evil angels penetrate our thoughts is a very hidden thing, and very difficult for men to discover and explain; thus he preferred suspending his judgment upon it, and remaining in doubt. Footnotes: [439] Matt. ii. 13,14. [440] S. Aug. lib. ii. retract. c. 30. CHAPTER LII. THE DIFFICULTY OF EXPLAINING THE MANNER IN WHICH APPARITIONS MAKE THEIR APPEARANCE, WHATEVER SYSTEM MAY BE PROPOSED ON THE SUBJECT.