There are limits, math theorems that cannot be proved within math. Ultimately we cannot know.
Seems like every discipline has things which we can know, things which we do not yet know, and things which we can never know.
Concerning the unknowable - in mathematics, we have Gödel's Incompleteness Theorems. In physics, we have Heisenberg's Uncertainty Principle. And in the historical sciences - evolution, archeology, anthropology, Egyptology - we have an incomplete record of evidence.
To me, all of these are cautions which attach to the value of evidence and/or work product - but not to the value of the discipline itself.