necessity. Orpheus proclaimed the need of the grace of the gods, Dionysus in particular, and of self-purification until the soul has completed the spiral ascent of destiny to live forever. An association between Pythagorean philosophy and reincarnation was routinely accepted throughout antiquity, as Pythagoras also taught about reincarnation. However, unlike the Orphics, who considered metempsychosis a cycle of grief that could be escaped by attaining liberation from it, Pythagoras seems to postulate an eternal, neutral reincarnation where subsequent lives would not be conditioned by any action done in the previous. Later authors In later Greek literature the doctrine is mentioned in a fragment of Menander and satirized by Lucian. In Roman literature it is found as early as Ennius, who, in a lost passage of his Annals, told how he had seen Homer in a dream, who had assured him that the same soul which had animated both the poets had once belonged to a peacock. Persius in his satires (vi. 9) laughs at this; it is referred to also by Lucretius and Horace. Virgil works the idea into his account of the Underworld in the sixth book of the Aeneid. It persists down to the late classic thinkers, Plotinus and the other Neoplatonists. In the Hermetica, a Graeco-Egyptian series of writings on cosmology and spirituality attributed to Hermes Trismegistus/Thoth, the doctrine of reincarnation is central. Celtic paganism In the first century BCE Alexander Cornelius Polyhistor wrote: Julius Caesar recorded that the druids of Gaul, Britain and Ireland had metempsychosis as one of their core doctrines: Diodorus also recorded the Gaul belief that human souls were immortal, and that after a prescribed number of years they would commence upon a new life in another body. He added that Gauls had the custom of casting letters to their deceased upon the funeral pyres, through which the dead would be able to read them. Valerius Maximus also recounted they had the custom of lending sums of money to each other which would are repayable in the next world. This was mentioned by Pomponius Mela, who also recorded Gauls buried or burnt with them things they would need in a next life, to the point some would jump into the funeral piles of their relatives in order to cohabite in the new life with them. Hippolytus of Rome believed the Gauls had been taught the doctrine of reincarnation by a slave of Pythagoras