How do we know any of this is true? If some of it is true, how do we know which parts are true? How would we find out if some of it is correct and some is wrong?

For instance, how do we know that our concept of self delimits what we can perceive rather than our actual self, defined as everything we are, including physics (at which point the statement is a tautology: we cannot perceive that which we cannot perceive)?

It might be irrational to perceive things contrary to one's sense of self, but we can't rely on that, as we can tell from how often people hold contradictory beliefs without feeling cognitive dissonance.