Cæsar, writing some fifty years before Christ about the Gauls and their Druids, tells his countrymen that one of the prime articles which they taught was that men's souls do not die--_non interire animas_--"but passed over after death from one into another," and their opinion is, adds Cæsar, that this doctrine "greatly tends to the arousing of valour, all fear of death being despised."[1] A few years later Diodorus Siculus wrote that one of their doctrines was "that the souls of men are undying, and that after finishing their term of existence they pass into another body," adding that at burials of the dead some actually cast letters addressed to their departed relatives upon the funeral pile, under the belief that the dead would read them in the next world. Timagenes, a Greek who wrote a history of Gaul now lost, Strabo, Valerius Maximus, Pomponius Mela, and Lucan[2] in his "Pharsalia," all have passages upon this vivid belief of the Gauls that the soul lived again. This doctrine must also have been current in Britain, where the Druidic teaching was, to use Cæsar's phrase, "discovered, and thence brought into Gaul," and it would have been curious indeed if Ireland did not share in it. There is, moreover, abundant evidence to show that the doctrine of metempsychosis was perfectly familiar to the pagan Irish, as may be seen in the stories of the births of Cuchulain, Etain, the Two Swineherds, Conall Cearnach, Tuan Mac Cairill, and Aedh Sláne.[3] But there is not, in our existing literature, any evidence that the belief was ever elevated into a philosophical doctrine of general acceptance, applicable to every one, still less that there was ever any ethical stress laid upon the belief in rebirth. It is only the mythological element in the belief in metempsychosis which has come down to us, and from which we ascertain that the pagan Irish believed that supernatural beings could become clothed in flesh and blood, could enter into women and be born again, could take different shapes and pass through different stages of existence, as fowls, animals, or men. What the actual doctrinal form of the familiar idea was, or how far it influenced the popular mind, we have no means of knowing. But as Mr. Nutt well remarks, "early Irish religion must have possessed some ritual, and what in default of an apter term must be styled philosophical as well as mythological elements. Practically the latter alone have come down to us, and that in a romantic rather than in a strictly mythical form. Could we judge Greek religion aright if fragments of Apollodorus or the 'Metamorphoses' were all that survived of the literature it inspired?"[4] The most that can be said upon the subject, then, is that the doctrine of rebirth was actually taught with a deliberate ethical purpose--that of making men brave, since on being slain in this life they passed into a new one--amongst the Celts of Gaul, that it must have been familiar to the Britons between whose