Marcus Annaeus Lucanus (d.65 CE) – otherwise known as Lucan – was a poet and author with close ties to the imperial court of Rome. He is best known for his description of the Roman Civil War in the 1stC BC, albeit more for its poetic rather than historical merit. Like Caesar, he commented on the druidic belief in the transmigration of souls:
While you, ye Druids, when the war was done,
To mysteries strange and hateful rites returned:
To you alone ’tis given the gods and stars
To know or not to know; secluded groves
Your dwelling-place, and forests far remote.
If what ye sing be true, the shades of men
Seek not the dismal homes of Erebus
Or death’s pale kingdoms; but the breath of life
Still rules these bodies in another age —
Life on this hand and that, and death between.
Happy the peoples ‘neath the Northern Star
In this their false belief; for them no fear
Of that which frights all others: they with hands
And hearts undaunted rush upon the foe
And scorn to spare the life that shall return.
(Translation by J.D. Duff: “Lucan: The Civil War”, Loeb Classics Library, London, 1928.)
It is possible he was quoting from Julius Caesar, yet almost a century after Caesar’s murder it still appears that the apparently core druidical doctrine of metempsychosis was contentious to Romans such as Lucan. The politics of the day was that the focus of the druidic religion had been pushed back into the Atlantic islands of Britannia and Hibernia, and Rome was in the process of its campaign of subjugating the former. Both Caesar and Lucan’s attitude towards the reincarnation doctrine was mirrored by other Roman writers such as Pomponius Mela (De Situ Orbiis c.43CE) who (like Lucan and Seneca) was from Roman Spain. These authors, along with Pliny the Elder, provided rhetorical accounts unkind to the religion of the druids during the period that Rome’s armies were pushing up through Britannia. A political reason to attack the core doctrine was that it was perceived that it rendered believers fearless of death.
Romans had no objection to the veneration of native gods in the territories they conquered, and must have actually created many as they went. The large number of remaining inscriptions and statuary items dedicated to these ‘Romano-Celtic’ deities in Britain is proof of this. It is a matter of conjecture, though, if these represented ancient original cults, especially as Roman historians and literary commentators during the first 100 years of Roman subjugation in Atlantic Europe indicated a Roman campaign against fundamental tenets of this style of religion, particularly the doctrine on metempsychosis.
It is quite likely that Romano-Gallic and Romano-British ‘deities’ were the result of an active campaign of interpretatio romanum designed to change the fundamental nature of local pagan belief to match one acceptable to the Mediterranean mindset of Rome (centred around their idea of ‘proper veneration’ of the ‘eternal gods’) and to the (often non-Roman) troops and auxiliaries it employed to do its dirty work in frontier provinces.
In Lucan’s time (middle of the 1stC CE) Ireland and the western and northern reaches of the ‘Britannic Isles’ would still have followed the doctrines that Julius Caesar wrote of after he had started to purge them in the 1stC BCE.