The “Stone” is described in the Rosary of Philosophers in oppositional terms : it “is miraculous and animated, splendid in colour, a Mountain sublime, and an open sea.” Would it be incorrect to consider “mountain sublime” and “open sea” epithetes? Are they metaphors, rather? I'd say they are epithets, but I've heard someone say they are metaphors instead. Apologies: this is not exactly an alchemy question, but your help would be very gratefully received.
I would say they are both, and that it depends on how the phrases are used:
If I say 'The Stone is a Mountain Sublime' I am speaking metaphorically (i.e. I am saying that the Stone is like a Mountain Sublime)
If I say 'The Philosophers sought to ascend the Mountain Sublime' then I am using an epithet (i.e. I am referring to the Stone as a Mountain Sublime because this phrase is generally understood to mean 'the Stone').
As far as I can tell, all epithets are metaphors, but not all metaphors are epithets.