Q: Perfect rationality is not humanly impossible.
A: Why so? If reason has failed you, then you have not been rational enough.
Q: Human beings are limited, so perfection remains forever beyond our grasp.
A: In what way are we limited?
Q: It is impossible for us to know everything, because the Universe is infinitely complex, and our brains are finite.
A: I grant we cannot know everything, but clear and logical thinking is not beyond our reach. An understanding of principles and the manifestation of that understanding in our lives is not impossible: this is what I mean by rationality.
Q: You are forgetting that human beings are emotional creatures as well as rational.
A: Yes, we experience emotion, but emotion is not something we have to put up with. One may be hungry, but need not remain so.