How do we know what we know?

[Silver]

You mean a process created by the human brain and performed by the human brain? It doesn't change the problem I outlined in the beginning of the OP

That's a problem between you and your brain, because my brain depends normally on empiricism.

Even then, an empiricist can accept one thing, and then 50 years when research develops and we realize that that one thing is false and a new thing is true, the empiricist was guilty of calling something a fact that wasn't. Not that I blame them, because I'd be in the same boat. If what we firmly think is true now is shown not to be in 50, 100, 150, etc. years... then that surely can't be objective knowledge or truth because we know it wasn't. So why call today's facts facts? 

That's the wonderful aspect of discernment between identifying as reasonable or religious. Despite the facts that back up my current empiricist view, my mind can always be changed when the proper evidence is provided. The same cannot be stated for those who are religious, for look how they attempt at altering science, intelligent design, in order to appease their biased religious views.

I suppose that's why we call very convincing scientific theories "Theories" regardless of the insane amount of evidence, but how many of us forget to be humble and assume what we think is true today is really, truly, objectively true?

Word salad.