We generally do not approach our questions this way. History is not a science. (And most scientific investigations, grade-school science fairs notwithstanding, do not actually proceed stepwise from hypotheses either, but that is a separate question.)

What we tend to make are interpretive arguments, which we support with evidence of various sorts (made visible through both citation and narrative), and which we argue against (if they are not ours) with other such evidence. Our evidentiary sources are deliberately broad, and we reserve the right to interrogate the methods of argumentation as well. We also generally do not presume to make arguments that are on the same level of universal scope (applies to all people/places/times) as of those in the natural sciences.

Hayden White's Metahistory is a very useful and important book in thinking about historical epistemology and narrative methodology, in my view. I would also note that poor ideas about how science works (which I suspect are often behind questions like this) do double-damage here: they hold up non-scientific disciplines to an impossible standard, by assuming that scientific disciplines follow that same standard. Neither are quite true, though the natural sciences do have different epistemological/methodological approaches than the social sciences, humanities, etc. (but they are often more varied than people who do not do or study science realize).