In ordinary dreams we do not judge the objects to be real;--we simply do not determine that they are unreal. The sensations which they seem to produce, are in truth the causes and occasions of the images; of which there are two obvious proofs: first, that in dreams the strangest and most sudden metamorphoses do not create any sensation of surprise: and the second, that as to the most dreadful images, which during the dream were accompanied with agonies of terror, we merely awake, or turn round on the other side, and off fly both image and agony, which would be impossible if the sensations were produced by the images. This has always appeared to me an absolute demonstration of the true nature of ghosts and apparitions--such I mean of the tribe as were not pure inventions. Fifty years ago, (and to this day in the ruder parts of Great Britain and Ireland, in almost every kitchen and in too many parlours it is nearly the same,) you might meet persons who would assure you in the most solemn manner, so that you could not doubt their veracity at least, that they had seen an apparition of such and such a person,--in many cases, that the apparition had spoken to them; and they would describe themselves as having been in an agony of terror. They would tell you the story in perfect health. Now take the other class of facts, in which real ghosts have appeared;--I mean, where figures have been dressed up for the purpose of passing for apparitions:--in every instance I have known or heard of (and I have collected very many) the consequence has been either sudden death, or fits, or idiocy, or mania, or a brain fever. Whence comes the difference? evidently from this,--that in the one case the whole of the nervous system has been by slight internal causes gradually and all together brought into a certain state, the sensation of which is extravagantly exaggerated during sleep, and of which the images are the mere effects and exponents, as the motions of the weathercock are of the wind;--while in the other case, the image rushing through the senses upon a nervous system, wholly unprepared, actually causes the sensation, which is sometimes powerful enough to produce a total check, and almost always a lesion or inflammation. Who has not witnessed the difference in shock when we have leaped down half-a-dozen steps intentionally, and that of having missed a single stair. How comparatively severe the latter is! The fact really is, as to apparitions, that the terror produces the image instead of the contrary; for 'in omnem actum perceptionis influit imaginatio,' as says Wolfe.