I believe the Interpretatio Romana (henceforth IR) was far more than a one way propaganda tool for the Roman invader. Instead, I think it may genuinely have been a sincere attempt at understanding, and in turn revering, a local indigenous deity albeit in a Romanized form. It was a testament to the cultural exchange and syncretism between the two cultures. Where some would see a Roman imposing his world view on the local populace, I see the Roman trying to understand and live in a new place or understand something new. What we have is a new way of looking a deity, which was the result of a fusion of two cultures (however imperfect).
The IR is particularly useful in our context because we have an interest in broadly speaking Romano-Celtic paganism and especially in how to revive this syncretistic process for the modern world. I think at the very least it provides us with evidence for where syncretism did actually occur. And it helps us to get a sense of the character of the deities we hope to honour and respect. Let’s take for example Sulis-Minerva; her shrine at Bath was extremely popular in the Ancient world. Her cult was older than the Roman temple built in her honour, but it was under Roman patronage that her cult grew and evolved to the point where she become internationally recognized. Sulis acquired many new traits by being syncretised with Minerva, and likewise Minerva’s character was changed through her association with this indigenous deity. So what we have is something new.
So, what role does the IR have today? It is an historical record for syncretism in the Ancient world (a roadmap), which is the ‘glue’ that holds a Romano-Celtic worldview together. What process did they use (most likely) in making these kinds of interpretations? This is something we will have to determine (as best we can). Can we do likewise today? This too is something that needs to given careful consideration.
The Nova Roma site states the following: “Eclecticism (as opposed to historical syncreticism; combining classical Roman religion with other cultural traditions that weren't combined historically; Romano-Celtic worship is certainly appropriate, sacrifice to Mercurius-Quetzalcoatl probably isn’t).” I agree that the half-hazard combining of cultures, deities, and the like is undesirable at best, but I don’t know whether or not the Roman mind would have combined Mercury with Quetzalcoatl. I don’t know enough about this Aztec god to know who would be his ‘best match,’ but I bet a Roman trying to better understand Quetzalcoatl would probably have used his own source culture to determine just that. In other words, using an IR would help him in relating to this new deity. So should we do likewise, especially where there is evidence for contact between these nations, or should we instead intentionally limit ourselves only to what examples we have in the historical record? Even where it doesn’t seem to be a good match-up? How much is too much and where do we draw the line?
That’s some of my thoughts on the topic. I look forward to hearing what people think.