And for the matter or substance of the invisible agents so fancied, they could not by natural cogitation fall upon any other conceit, but that it was the same with that of the soul of man; and that the soul of man was of the same substance with that which appeareth in a dream to one that sleepeth; or in a looking-glass, to one that is awake; which, men not knowing that such apparitions are nothing else but creatures of the fancy, think to be real and external substances, and therefore call them ghosts: as the Latins called them “imagines” and “umbrae,” and thought them spirits, that is, thin aerial bodies, and those invisible agents which they feared to be like them, save that they appear and vanish when they please.