^^^^
Not while remaining faithful to their religion. A core tenant of all three faiths you named is that their God (which are all different interpretations of the same god) is the ONLY god and you cannot recognize any other god.
Of course, there have always been varying interpretations of each faith. Christianity, especially, has lent itself to syncretism quite well. There have been (and still are) many cultures where the people would identify themselves as Christian, but see no contradiction in also recognizing aspects of other faiths, including sometimes gods (although they might call them some other word).
If you’re following any of the major, world-recognized denominations of Christianity, Judaism, or Islam (eg Catholicism, Protestantism, Sunni Islam, Orthodox Judaism, Shia Islam, etc) then, no, you cannot worship pagan gods. But there are smaller versions of each religion which do.
Everyone can pray to what or whomever they like.
I love how that part admits that there are other gods.
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Jewish law doesn’t apply to gentiles, for good or ill.,
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“Before.”
Now the mystic branches of these religions have a different interpretation, to lesser and greater degrees. The fanatics in each would kill them all.
Yes, I think as a pure theological question, historical thought has been a bit complicated. So I linked to the Wikipedia article that hopefully goes into it a bit. I admit to not having read the Wikipedia article carefully. This isn’t my area at all.
Wikipedia takes the politicized view. Probably because Israel was occupied by Rome, and Constantine liked it. There are some views that say Christianity was invented by Jews for Rome, and there’s certainly no evidence for a singular, historical Jesus, to the best of my knowledge. Nonetheless, the Nicean council left out plenty, but left in some the lore that would be explained by and expounded on the books excluded. Probably again d/t Roman political purview.
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