More than 30 Greek and Roman writers from around 200 BCE to the 4th century CE were fascinated by this enigmatic group of ritualists. There has been a lot of controversy concerning the veracity of these ancient authors and their plagiarism or recycling of ‘facts’ about the Druids. However, I do have faith in one: Julius Caesar. He was in Gaul for nearly 10 years in the 50s BCE, leading the war of Roman conquest and so he knew the region personally rather than relying on secondhand information. And, because he was writing his chronicle for scrutiny by the Senate in Rome, it is doubtful whether he would have got away with fanciful imaginings because they could have been contradicted by his fellow officers.
https://aeon.co/essays/what-can-archaeo ... -dark-arts
