Lucian[55] tells us that it was only with Pluto's permission that the dead could return to life, and they were invariably accompanied by Mercury. Consequently, both these gods were regularly invoked in the prayers and spells used on such occasions. Only the souls of those recently dead were, as a rule, called up, for it was naturally held that they would feel greater interest in the world they had just left, and in the friends and relations still alive, to whom they were really attached. Not that it was impossible to evoke the ghosts of those long dead, if it was desired. Even Orpheus and Cecrops were not beyond reach of call, and Apollonius of Tyana claimed to have raised the shade of Achilles.[56]

All oracles were originally sacred to Persephone and Pluto, and relied largely on necromancy, a snake being the emblem of prophetic power. Hence, when Apollo, the god of light, claimed possession of the oracles as the conqueror of darkness, the snake was twined round his tripod as an emblem, and his priestess was called Pythia. When Alexander set up his famous oracle, as described by Lucian, the first step taken in establishing its reputation was the finding of a live snake in an egg in a lake. The find had, of course, been previously arranged by Alexander and his confederates.

We still possess accounts of the working of these oracles of the dead, especially of the one connected with the Lake of Avernus, near Naples. Cicero[57] describes how, from this lake, "shades, the spirits of the dead, are summoned in the dense gloom of the mouth of Acheron with salt blood"; and Strabo quotes the early Greek historian Ephorus as relating how, even in his day, "the priests that raise the dead from Avernus live in underground dwellings, communicating with each other by subterranean passages, through which they led those who wished to consult the oracle hidden in the bowels of the earth." "Not far from the lake of Avernus," says Maximus of Tyre, "was an oracular cave, which took its name from the calling up of the dead. Those who came to consult the oracle, after repeating the sacred formula and offering libations and slaying victims, called upon the spirit of the friend or relation they wished to consult. Then it appeared, an unsubstantial shade, difficult both to see and to recognize, yet endowed with a human voice and skilled in prophecy. When it had answered the questions put to it, it vanished." One is at once struck with the similarity of this account to those of the spiritualistic séances of the famous Eusapia in the same part of the world, not so very long ago. In most cases those consulting the oracle would probably be satisfied with hearing the voice of the dead man, or with a vision of him in sleep, so that some knowledge of ventriloquism or power of hypnotism or suggestion would often be ample stock-in-trade for those in charge.

This consulting of the dead must have been very common in antiquity. Both Plato[58] and Euripides[59] mention it; and the belief that the dead have a knowledge of the future, which seems to be ingrained in human nature, gave these oracles great power. Thus, Cicero tells[60] us that Appius often consulted "soul-oracles" (psychomantia), and also mentions a man having recourse to one when his son was seriously ill.[61] The poets have, of course, made free use of this supposed prophetic power of the dead. The shade of Polydorus, for instance, speaks the prologue of the Hecuba, while the appearance of the dead Creusa in the Æneid is known to everyone. In the Persæ, Æschylus makes the shade of Darius ignorant of all that has happened since his death, and is thus able to introduce his famous description of the battle of Salamis; but Darius, nevertheless, possesses a knowledge of the future, and can therefore give us an equally vivid account of the battle of Platæa, which had not yet taken place. The shade of Clytemnestra in the Eumenides, however, does not prophesy.

Pliny mentions the belief that the dead had prophetic powers, but declares that they could not always be relied on, as the following instance proves.[62] During the Sicilian war, Gabienus, the bravest man in Cæsar's fleet, was captured by Sextus Pompeius, and beheaded by his orders. For a whole day the corpse lay upon the shore, the head almost severed from the body. Then, towards evening, a large crowd assembled, attracted by his groans and prayers; and he begged Sextus Pompeius either to come to him himself or to send some of his friends; for he had returned from the dead, and had something to tell him. Pompeius sent friends, and Gabienus informed them that Pompeius's cause found favour with the gods below, and was the right cause, and that he was bidden to announce that all would end as he wished. To prove the truth of what he said, he announced that he would die immediately, as he actually did.

This knowledge of the future by the dead is to be found in more than one well-authenticated modern ghost story, where the apparition would seem to have manifested itself for the express purpose of warning those whom it has loved on earth of approaching danger. We may take, for instance, the story[63] where a wife, who is lying in bed with her husband, suddenly sees a gentleman dressed in full naval uniform sitting on the bed. She was too astonished for fear, and waked her husband, who "for a second or two lay looking in intense astonishment at the intruder; then, lifting himself a little, he shouted: 'What on earth are you doing here, sir?' Meanwhile the form, slowly drawing himself into an upright position, now said in a commanding, yet reproachful voice, 'Willie! Willie!' and then vanished." Her husband got up, unlocked the door, and searched the house, but found nothing. On his return he informed his wife that the form was that of his father, whom she had never seen. He had left the navy before this son was born, and the son had, therefore, only seen his father in uniform a very few times. It afterwards came out that her husband was about to engage in some speculations which, had he done so, would have proved his ruin; but, fortunately, this vision of his father made such an impression on him that he abandoned the idea altogether.

Lucan[64] describes how Sextus Pompeius went to consult Erichtho, one of the famous Thessalian witches, as to the prospects of his father's success against Cæsar, during the campaign that ended in the disastrous defeat at Pharsalia. It is decided that a dead man must be called back to life, and Erichtho goes out to where a recent skirmish has taken place, and chooses the body of a man whose throat had been cut, which was lying there unburied. She drags it back to her cave, and fills its breast with warm blood. She has chosen a man recently dead, because his words are more likely to be clear and distinct, which might not be the case with one long accustomed to the world below. She then washes it, uses various magic herbs and potions, and prays to the gods of the lower world. At last she sees the shade of the man, whose lifeless body lies stretched before her, standing close by and gazing upon the limbs it had left and the hated bonds of its former prison. Furious at the delay and the slow working of her spells, she seizes a live serpent and lashes the corpse with it. Even the last boon of death, the power of dying, is denied the poor wretch. Slowly the life returns to the body, and Erichtho promises that if the man speaks the truth she will bury him so effectually that no spells will ever be able to call him back to life again. He is weak and faint, like a dying man, but finally tells her all she wishes to know, and dies once again. She fulfills her promise and burns the body, using every kind of magic spell to make it impossible for anyone to trouble the shade again. Indeed, it seems to have been unusual to summon a shade from the lower world more than once, except in the case of very famous persons. This kind of magic was nearly always carried on at night. Statius[65] has also given us a long and characteristically elaborate account of the calling up of the shade of Laius by Eteocles and Tiresias.

Apuleius,[66] in his truly astounding account of Thessaly in his day, gives a detailed description of the process of calling back a corpse to life. "The prophet then took a certain herb and laid it thrice upon the mouth of the dead man, placing another upon the breast. Then, turning himself to the east with a silent prayer for the help of the holy sun, he drew the attention of the audience to the great miracle he was performing. Gradually the breast of the corpse began to swell in the act of breathing, the arteries to pulsate, and the body to be filled with life. Finally the dead man sat up and asked why he had been brought back to life and not left in peace."

One is reminded of the dead man being carried out to burial who meets Dionysus in Hades, in Aristophanes' Frogs, and expresses the wish that he may be struck alive again if he does what is requested of him. If ghosts are often represented as "all loath to leave the body that they love," they are generally quite as loath to return to it, when once they have left it, though whether it is the process of returning or the continuance of a life which they have left that is distasteful to them is not very clear. The painfulness of the process of restoration to life after drowning seems to favour the former explanation.