It's not that I don't know what contemporary means.
It's just that in my specific sentence (below) I'm not sure if it could be ambiguous. If it is ambiguous, then I'm looking for a word or phrase to substitute for 'contemporary' that makes it clear that the pagan philosophers lived at a time when Christianity was still in its infancy. Here's the sentence:
And that’s what the early modern readers of Celsus, Porphyry and Julian were bent on discovering: how early Christianity was perceived and judged by contemporary pagan philosophers.
'Contemporary' is meant to refer to the pagans of antiquity, not of the early modern period (and certainly not modern-day pagans). Is this clear? Would 'coeval' make it any clearer?
And that’s what the early modern readers of Celsus, Porphyry and Julian were bent on discovering: how early Christianity was perceived and judged by coeval pagan philosophers.
Or do I have to completely changed the sentence to be unambiguous:
And that’s what the early modern readers of Celsus, Porphyry and Julian were bent on discovering: how early Christianity was perceived and judged by the pagan philosophers who witnessed its birth and infancy.
(I would prefer not to have to use the last sentence, since my sentence is a translation from German and I would prefer to stay more closely to the original text.)