In popular phrase, however, the two last kinds of apparitions are called 'ghosts,' or 'wraiths,' and the popular tendency is to think of these, and of these alone, when 'apparitions' are mentioned. On the other hand the tendency of common-sense is to rank the two last sorts of apparition, the wraith and ghost, with all the other kinds, which are undeniably caused by accident, by malady, mental or bodily, or by mere confusion and misapprehension, as when one, seeing a post in the moonlight, takes it for a ghost. Science, following a third path, would class all perceptions which 'have not the basis in fact that they seem to have' as 'hallucinations'. The stars seen after a blow on the eye are hallucinations,--there are no real stars in view,--and the friend, whose body seems to fill space before our sight when his body is really on a death-bed far away;-- and again, the appearance of the living friend whom we see in the drawing-room while he is really in the smoking-room or in Timbuctoo,--are hallucinations also. The common-sense of the matter is stated by Aristotle. 'The reason of the hallucinations is that appearances present themselves, not only when the _object of sense_ is itself in motion, but also when the _sense_ is stirred, as it would be by the presence of the object' (De Insomn., ii. 460, b, 23- 26). The ghost in a haunted house is taken for a figure, say, of a monk, or of a monthly nurse, or what not, but no monthly nurse or monk is in the establishment. The 'percept,' is a 'percept,' for those who perceive it; the apparition is an apparition, for _them_, but the perception is hallucinatory.