HA, your objection is too vague for me to apply. Specify.

But if we were minds in a vat, or cogs in the Matrix, we would still be able to reason rationally and make intelligent predictions about the world we see. And test them, and improve our predictions and discard the ones that are wrong. We can be rational about the real world, even if the real world is an illusion.

I do not understand your bizarre concept, illusion. Whatever is, is real. Sometimes the underlying levels of organization are different from what you expected.

So I don't see how we can found rationality on our understanding of the world (a world we only understand through reason). In this argument, where is the egg that was not born of a chicken?

That's why I distinguished deliberate rationality. Seeing your shoelaces is also rational, for it produces beliefs that are themselves evidence; but it is not a process that requires deliberate control. The lens sees, even in mice; but only in humans does the lens see itself and see its flaws.