What is rationality?
It is the capability to think along the rules of common logic and to act accordingly. To be a rational person requires to reflect one’s own experience.
Why to prefer rationality over irrationality?
Experience shows that rationality decreases the probability of error and allows to learn from one’s mistakes. In particular to avoid the principle “The wish is the father of the thought.”
Why to dismiss mysticisms as justification for believes?
Mysticism often indicates that the real mechanism behind the phenomenon has not yet been detected. AcceptingTo welcome mysticism stops further research.
All of these answers need further discussion and elaboration.