Socrates is one of the most well know ln philosophers of all time and there isn’t any proof he ever lived.

when is the fact about the level of certainty we have about Socrates’s existence relevant, though? it depends.

• if someone just mentions some specific idea that is often attributed to Socrates, then it’s probably totally irrelevant and you would be just "well, actually"ing someone. (which will backfire esp. if they actually know that full well and can/will stand for themselves)

• if someone is defending a specific idea using an argument from authority of Socrates himself, then it’s probably pretty relevant. at best it’s an invitation to skip a bad argument path and take the focus back to the potential merit of the idea itself. (ofc this is regardless of whether you like that idea or not, learning what the other person perceive as valuable about the idea is usually more interesting than who they think came up with it)

• if someone does the same but based on moral authority, then it’s the same principle, but probably much more important

• if someone creates religion based on teachings of Socrates, then it’s pretty much important (although often seemingly ineffective, and in some cases, risky)

• If someone starts asking questions about Socrates as a historical person (and heck, even questions specifcally about history of Socrates’ state of mind–see title of this whole post), then it’s obviously the most important thing they need to learn before continuing their research or pondering.

The last point bullet point describes what @Phoenixz did here, in the beginning of this sub-thread. (Just for Jesus Christ, not Socrates, of course.)