Homer seems to allude to this, when he makes Patroclus's Ghost appear to Achilles. When Patroclus was slain by Hector before Troy, the Body, after a long Dispute for it, between the Greeks and Trojans, was brought to Achilles's Tent, where Achilles is described by the Poet, as making bitter Lamentations over the Body of his deceased Friend. At Night he lays himself down upon the Sea Shore, and falls asleep, when the Ghost of Patroclus comes to demand the funeral Obsequies. [Greek: Êlthe d' epi psuchê Patroklêos deiloio,] [Greek: Pant' autôi megethos te kai ommata kal' eikuia,] [Greek: Kai phônên; kai toia peri chroi heimata hesto;] Hom. Iliad. Lib. 23. Homer never introduces an Incredulus Odi into his Works; he has an Eye upon Probability in all his Fictions. It seems probable, that Achilles, after he had been hanging over the Body of Patroclus, either quite asleep, or between sleeping and waking, should imagine that he saw his Friend's Apparition. And though Homer might not have heard of such a Thing as the Retina in the Eye, (though it is not at all impossible he should, for he shews himself a great Anatomist) yet he very well knew the Impression which the Sight of a departed Friend is sure to make upon the Mind of the Beholder. By this Propriety of Introduction, he keeps up the Appearance of Probability, so necessary even in Poetry itself, which is generally Fiction. By this it should seem, that Homer was tacitly of Opinion, that there is really no such Thing in Nature as an Apparition, and that it has no other Existence than in the Imaginations of Men. And we have the more Reason to believe that this was his Opinion, as we find that he did not choose to introduce the Ghost of Patroclus to Achilles, when he was broad awake; but, as he thought it might seem to want the Air of Probability, if he made Patroclus appear to Achilles when awake, he takes Care to compose Achilles into a Nap first, and by that means leaves the Reader to his own Opinion, whether the Ghost did really come, or whether Achilles only thought so. This is one of those Touches of Art with which Homer abounds. But there is another Reason why we have so many of these Stories told us of Apparitions by our Grandmothers; and that is, the Tricks which the Priests of the Roman Catholic Times found it necessary to put upon their Flock, in order to keep up their Credit.