I know assuredly, that Janet Douglas, that was first a dumbie, yet spoke thereafter, who had given many responses by signs and words, and foretold many future events, being examined by Mr Gray, one of the ministers of the city of Glasgow, denied any explicitor implicit paction, and declared freely, that the answers of the questions proponed to her were represented by a vision in lively images, representing the persons concerned, and acting the thing, before her eyes. This Mr Gray exchanged several discourses in write with Sir James Turner, concerning her.

By this time, you may see that this theme deserves the consideration of the learned: First, to enquire how much of this may come from a natural constitution and temperament, when confounded with a flatuous or melancholic distemper; and what influence an external agent, namely, an angel, good or bad, may have upon the organ of the eye and the fancy, and how far the medium between the organ of the eye and an object visible, may be disposed for their purpose, namely, the air and light; and what connexion may be found betwixt the representations made to the eye or fancy, and the future contingent events that experience teaches do follow thereupon: as for example, a man is seen bleeding, or sewed up in his winding sheets, who is shortly to be wounded, or assuredly to die.

As for the first, all the learned physicians of the world know too well by experience what great labour they have to cure the deceptions of the fancy, especially in hypochondriac diseases; nay, patients cannot be persuaded but they see men, women, fowls, and four-footed beasts, walking abroad or in their chambers. Seldom it is, that a man passes any great and turbulent fever, without the trouble of some such representations. It is memorable, that a gentleman, that had been a great proficient in physic himself, imagined at length that there was a quick frog in his belly; and after he had travelled over a good part of Italy, and consulted with the doctors of Padua, yet could not be cured, or dissuaded. He came at length to the learned physician Platerus, in Bazil, who told him, that a frog by certain experience is known not to live above three years, so that his distemper continuing longer than three years, could not be caused by the frog, that could not live so long. Moreover, that his stomach would strangle the frog, and that the frog could not live any considerable time out of its own element, the water; so that the properest and most specific medicines being made use of, it were a shame for him to be so obstinate. At last he was persuaded, and his fancy satisfied. This story is no less renowned of what befell Andreas Osiander, a man learned in most languages. When he was a young man, and being troubled with a quartan ague, a little before the fit he could not be persuaded that he was in the house at all, but that he was in a wood, and much molested with wild beasts and serpents of all kinds; neither could he be prevailed with that this was false, till Facius Cardanus was called for to him, who cured him for the time, so that he knew his friends that were sitting beside him, and the chamber to be his own chamber; but after Facius had left him, he was troubled with the same opinion and distemper, even till the ague had quiet him. I have myself seen a neighbour of my own, and my parishioner too, John M'Phale, that lived to the age of fourscore years, a man that was truly very sagacious by nature; and though his sight was much decayed, the seat of his judgment was nothing touched; and as he grew weaker, merely by old age, without any remarkable distemper, I made frequent visits to him. One day as I was coming away from him, he told me he had something of consequence to ask at me, and desired all to remove except his wife and another gentleman, that was a friend of his. This done, Sir, says he, I desire to know by what warrant or commission so many of my friends, that are dead long ago, are allowed to come and discourse with me, and drink before me, and yet are not so civil as give me a tasting of it? I told him, that it was only the trouble of his fancy, and his frequent thinking of the world to come and his friends that were gone before him; and he replied to me very smartly, Sir, says he, I perceive it is the work of the fancy, for since I cannot see yourself, (for only by your voice I know you) how could I see them? It was strange that he saw them the very mean time that others were in the house with him, and asked several questions at them, but got no answer. And, for all this, the seat of his wit was as entire as ever: moreover, this trouble left him a little before he died.

Many such illusions are reported of eremites, caused merely by the confusion of the brains, bred by their fasting and unwholesome food, which I shall not trouble the reader with.

If you will ask how cometh this to pass, take notice of the following method, which I humbly offer to your consideration. Advert, in the first place, that visible ideas, or species, are emitted from every visible object to the organ of the eye; representing the figure and colour of the object, and bearing along with it the proportion of the distance, for sure the objects enter not the eye, nor the interjacent distant tract of ground; and a third thing different from the eye and the object, and the distant ground, must inform the eye. These species are conveyed to the brain by the optic nerve, and are laid up in the magazine of the memory, otherwise we should not remember the object any longer than it is in our presence; and a remembering of these objects is nothing else but the fancies reviewing, or more properly the soul of man, by the fancy reviewing of these intentional species formerly received from the visible object unto the organ of the eye, and reconducted unto the seat of the memory. Now, when the brain is in a serene temper, these species are in their integrity, and keep their rank and file as they were received; but when the brain is filled with gross and flatuous vapours, and the spirits and humour enraged, these ideas are sometimes multiplied as an army, by mist; sometimes magnified, sometimes misplaced, sometimes confounded by other species of different objects, perhaps by half and half, so that the fancy has two for one, one bigger than two of itself, and sometimes the half of one and the half of another, represented in one; and this deception is not only incident to the fancy, but even to the external senses, particularly the seeing and hearing; for the visus, or seeing, is nothing else but the transition of the intentional species through the crystalline humour to the retiform coat of the eye, and judged by the common sense, and conveyed by the optic nerve to the fancy.

Of this we have a clear demonstration from the representation of external objects through a crystal in glass, upon any lucid, smooth, and solid reflectant, placed before the glass in a dark chamber, which is one of the noblest experiments in the whole optics.

Now, if these species formerly received and laid up in the brain, will be reversed back from the same to the retiform coat and crystalline humour as formerly, these is in effect a lively seeing and perception of the object represented by these species, as if, de novo, the object had been placed before the eye; for the organ of the eye had no more of it before, than now it has; just so with the hearing, it is nothing else but the receiving of the audible species to that part of the ear that is accommodated for hearing, so that when the species are retracted from the brain to their proper organs, for example, the ear and the eye, hearing and seeing are perfected, as if the objects had been present to influence the organs de novo. And it is not to be thought that this is a singular opinion, for Cardanus, an eminent author of great and universal learning and experience, maintains this reversion of the species, and attributes his own vision of trees, wild beasts, men, cities, and instructed battles, musical and martial instruments, from the fourth to the seventh year of his age, to the species of the objects he had seen formerly, now retracted to the organ of the eye, and cites Averroes, an author of greater renown for the same opinion. See Cardanus de subtilitate rerum pagina trecentesima prima.

And it seems truly to be founded upon relevant grounds. I have observed a sick person, that complained of great pain and molestation in his head, and particularly of piping and sweating in his ears, which seems to have been caused by the species of piping and singing which he had formerly heard, but were now, through the plethory of his head, forced out of the brain to the organ of the ear, through the same nerves by which they were received formerly; and why may not the same befall the visible species as well as the audible? which seems to be confirmed by the optic experiment. Take a sheet of painted paper and fix it in your window, looking steadfastly to it for a considerable time, for example, some few minutes, then close your eyes very strait, and place a sheet of clean paper before your eyes, and open your eyes suddenly, you will see the painting almost as lively as they were in the painted sheet with the lively colours. This compression of the eyes by consent, causes a compression of the whole brain, which forces back the visible species of the painted sheet to the organ of the eye, through the optic nerve, which will presently vanish, if the reflectant did not help to preserve them. You may see then how much of these representations may be within ourselves, abstracting from any external agent or object without the eye, to influence the same.

The second thing that comes under consideration is, the influence and operation of external agents, namely, an angel, good or bad. It is not to be denied, but good angels may help and dispose all our faculties, excite, elevate, and set them upon edge and action; likewise, that evil angels may perturb, confound, and hurt, our external and internal senses, (when permitted) particularly by stirring the spirits, humours, and vapours, which of themselves, when so stirred, help to make many shapes and representations, either regular or irregular, (as has been formerly observed) and withal, they can colorate external objects far beyond any painter, insensibly to the beholder, repente applicando activa passivis; and that they can alter the medium interposed between our senses and the objects, by making it grosser or thinner, opaque or lucid, is a thing not to be questioned. For a clear proof of this I hope any rational man will allow me.