Regardless, I suppose the bigger point I want to make is the truth for non clear cut things is only as true as the number of people that co-sign it. If there’s simply more people on one side, welp, that’s that. That’s the truth, as far as we know.
Right or wrong or true or false are almost not even in the equation (enter the conspiracy theorist).
I don’t know, based on what I just said, what do you believe?
You see?
Examples:
* Multiple attestation. Do we have multiple independent sources telling us the same thing?
* Contextual credibility. Do people behave in a way that's plausible given their setting (the languages they spoke, what they knew at the time).
* Embarrassment. Is this detail actually inconvenient for the person relaying it (and not the sort of thing they'd make up)?
see "Criteria of authenticity" in https://en.wikipedia.org/wiki/Quest_for_the_historical_Jesus
Why is this an important question at all?
I just plucked it out of the air as a historical event that took place a long time ago and occured in a culture with written history. It has no particular importance in the abstract (though the British and French do still seem to talk about it more than one would expect).
But there's something required beforehand: definining what this or that is. It's not really a subjective process, but it certainly isn't objective either.
Before you can decide whether or not William the Conqueror's invasion of the British Isles was a good or a bad thing, you first need a description of how the invasion was carried out and "all" the consequences. But there is no "objective" or "clear cut" version of this. What do you include? What do you exclude?