I'll admit that we are infinitely ignorant, and endlessly fallible, and thus we can never be sure that we've reached the truth, regardless of what it is. But we do have our best explanations, and we must live and act as if those best explanations are true, because there is nothing else we can do. Epistemologies like Bayesianism are very popular today, but those never made much sense to me. We have the best most useful explanations until they are falsified, and even then they remain useful approximations, like Newton's Gravity being replaced by Einstein's. The reason Newton's is still a good approximation is because it was our best explanation at one time, and good explanations are good for a reason. They are falsifiable, and therefore testable, and they are hard to vary, and therefore fully explain the phenomena they reference. One day, Einstein's theory will also be replaced, or absorbed into Quantum theory, and one day even Quantum theory will be replaced. We will never have the final ultimate explanation, but we will always be able to create closer and closer approximations to the truth. Even if we did discover the final ultimate theory of something, we would never know it to be so.

This theory of the mind and universal explanation may indeed be wrong, but I would strongly suggest it is our current best explanation, and should be acted on as such. It can easily be falsified by discovering a completely new mode of explanation that is out of our reach, or by building an ASI that has a qualitative gain on us. I hope I'm alive for that because it'll be a very exciting time! :)