M. D’Arbois maintains that, as a result of persecution, the Druids retired to the depths of the forests, and continued to teach there in secret those who despised the new learning of Rome, basing his opinion on passages of Lucan and Mela, both writing a little after the promulgation of the laws.[1074].  But neither Lucan nor Mela refer to an existing state of things, and do not intend their readers to suppose that the Druids fled to woods and caverns.  Lucan speaks of them dwelling in woods, i.e. their sacred groves, and resuming their rites after Caesar’s conquest not after the later edicts, and he does not speak of the Druids teaching there.[1075] Mela seems to be echoing Caesar’s account of the twenty years’ novitiate, but adds to it that the teaching was given in secret, confusing it, however, with that given to others than candidates for the priesthood.  Thus he says:  “Docent multa nobilissimos gentis clam et diu vicenis annis aut in specu aut in abditis saltibus,"[1076] but there is not the slightest evidence that this secrecy was the result of the edicts.  Moreover, the attenuated sacrificial rites which he describes were evidently practised quite openly.  Probably some Druids continued their teaching in their secret and sacred haunts, but it is unlikely that noble Gauls would resort to them when Greco-Roman culture was now open to them in the schools, where they are found receiving instruction in 21 A.D.[1077] Most of the Druids probably succumbed to the new order of things.  Some continued the old rites in a modified manner as long as they could obtain worshippers.  Others, more fanatical, would suffer from the law when they could not evade its grasp.  Some of these revolted against Rome after Nero’s death, and it was perhaps to this class that those Druids belonged who prophesied the world-empire of the Celts in 70 A.D.[1078] The fact that Druids existed at this date shows that the proscription had not been complete.  But the complete Romanising of Gaul took away their occupation, though even in the fourth century men still boasted of their Druidic descent.[1079]

The insular Druids opposed the legions in Southern Britain, and in Mona in 62 A.D. they made a last stand with the warriors against the Romans, gesticulating and praying to the gods.  But with the establishment of Roman power in Britain their fate must have resembled that of the Druids of Gaul.  A recrudescence of Druidism is found, however, in the presence of magi (Druids) with Vortigern after the Roman withdrawal.[1080] Outside the Roman pale the Druids were still rampant and practised their rites as before, according to Pliny.[1081] Much later, in the sixth century, they opposed Christian missionaries in Scotland, just as in Ireland they opposed S. Patrick and his monks, who combated “the hard-hearted Druids.”  Finally, Christianity was victorious and the powers of the Druids passed in large measure to the Christian clergy or remained to some extent with the Filid.[1082] In popular belief the clerics had prevailed less by the persuasive power of the gospel, than by successfully rivalling the magic of the Druids.