I'm not clear on your initial premise, as different sources will describe the term differently, from an evil twin to a body double. I'm inclined to accept the latter definition, because who's to say, assuming that you're the original, that you're not the evil one? How would the existence of a body double, or doppelganger, delineate one's good half from their evil half? If it's carbon copy of you, and you are both good and evil, how is the double not also a mix of the two? Sounds like you've picked a very difficult puzzle to solve and I wish you luck.

Reminds me of the Native American parable of the two wolves:

A grandfather is talking with his grandson and he says there are two wolves inside of us which are always at battle.

One is a good wolf which represents things like kindness, bravery, and love. The other is a bad wolf, which represents things like greed, hatred, and fear.

The grandson stops and thinks about it for a second then he looks up at his grandfather and says, “Grandfather, which one wins?”

The grandfather quietly replies, “The one you feed.”

Plausible deniability and accountability, if you feel like you have an out you take it, in essence to the nature of man.

It’s similar to the concept of changelings too, in that the soul can’t be mimicked but the flesh can. Though that was more of a way to primitively understand autism and mental illness manifesting in toddlers.

The key is not to defeat one or the other, but to learn to live with both

No, l don't speak any foreign languages.

Nope.

But this guy that looks just like me probably does.

Okay you're approaching it as an archetype, either psychologically or literarily.

[ancient-origins.net]

It's worthwhile to include the mythological aspect of the idea as part of its formation as a social archetype or as etymological origin. Should at least be good for a few lines of 'let's stretch this an extra page.'

I always wrote the paper that said what i wanted to say, and then spent many hours adding in a paragraph here or a line here. That way you're only WRITING writing for about 8 or 9 hours, and the other several hours are spent integrating evidence and supporting statements from cited sources in layers. It helps break up the hours on concentration into a series of more manageable 20 minute - 1 hour tasks, while also allowing you to edit on the fly and rearrange as needed. I wrote a lot of papers the night they were due.

It's metaphorical. In an original Star Trek episode, Kirk is split into two, his good side and his bad, which in reality, isn't prone to happen. The conflict is when the two sides meet and how the conflict is resolved, which can be typically messy. The isn't necessarily an intent to resolve the differences, rather, it's just an examination of where it can go.