Descartes, though I find his answer silly, deserves substantial accolades for asking the question "What can we be certain of?". Asking the question is usually the hard part.
Hume deserves the title of greatest epistemologist ever, for the first decent answering of the question. His answer, of course, is nothing. The fundamental line in Hume is that belief is EITHER about imaginary items (Math) or not certain.
Many many unsatisfactory responses followed.
And then Bayes asked a better question: How certain should I be of a given belief? And then he answered it. The math is simple.
So what does that lead us to...
It means that we can mathematically decide not only what beliefs to have (based on experience), but also how certain we should be of those beliefs. If we pretend rationality, then belief is no longer a question of preference, but rather of evidence + math. I believe what I want defines irrationality.
There are other paths. One can believe as one wishes, without pretending that the beliefs are subject to reason. Reason is merely one epistemic foundation. And I'm not entirely convinced that it's the best one for most people most of the time. It's certainly the hardest. And for an awful lot of folks...it gives less good answers than social epistemology does 9 times out of 10.
One can trust another person...and accept their conclusions, as they are better than one's own. This, like general social epistemology, will give better results than reason for 50+% of the people.
One can not believe much of anything...and wear beliefs as clothes. Beliefs, fundamentally, are properly about getting what you want/need, not about truth. This is highly under-rated as a method.
If one chains oneself to rationality, one has no room to believe in those things one wants...but rather one is forced to conditional belief in many things. If one believes from some other option, those are highly adaptive strategies as well. One's beliefs, then, are constrained elsewhere.