Especially as you go further back contemporary records get scarce at best. What allows us to know that Alexander the Great was a real person? Or Ramesses II or Sargon of Akkad?
This is less a question about these specific people and more about methodology. I'm not asking "Was Caesar fake?" I'm asking "How do we know he was real?"
If its just "A lot of contemporary sources talk about the person" how do we separate literary/mythological figures from real ones?
Hello, This question digs at the heart of Historiography and the Historical Profession itself. The thing with this question though is that it does make one crucially wrong assumption:
It assumes that we can ever fully KNOW if a person existed.
Philosophically that is a contentious idea and for the Historical Profession, it is doubly so. History is never about getting the absolute correct answer but rather the best answer with available information. When we are trying to decide if a person existed we look at primary and first-hand evidence to make an initial induction about if they existed. If there isn't enough evidence then how can anyone know that they existed? Every historical figure (even the most well-known ones) can only ever be at most a best guess at existence because new information in historiography doesn't prove if a person existed but rather updates our confidence that they did or didn't.
But to help with understanding this, here is usually how I in my historical work judge the authenticity of a person or fact.
Even if all 5 points are accounted for and they boost my confidence of that person existing, it never gets to full certainty.
Also, note that Secondary and tertiary sources tend to never come up in proving the authenticity of something because you don't inspect the foundation of a building by looking at its antennas.
Anyway, I hope this answers your question. I will be answering any relevant questions in the comments.
Seth,
(Edits for Grammatical Errors and rephasing some things)