Motivation stems from doubt.

from Zen and the Art of Motorcycle Maintenance by Robert Pirsig page 152 fiction ~1 min read

The lecture notes explain almost all of why he acted the way he did, but leave one thing unexplained...his fanatic intensity. One can believe in the truth and in the process of reason to discover it and in resistance to state legislatures, but why burn one's self out, day after day, over it?

The psychological explanations that have been made to me seem inadequate. Stage fright can't sustain that kind of effort month after month. Neither does another explanation sound right, that he was trying to redeem himself for his earlier failure. There is no evidence anywhere that he ever thought of his expulsion from the university as a failure, just an enigma. The explanation I've come to arises from the discrepancy between his lack of faith in scientific reason in the laboratory and his fanatic faith expressed in the Church of Reason lecture. I was thinking about the discrepancy one day and it suddenly came to me that it wasn't a discrepancy at all. His lack of faith in reason was why he was so fanatically dedicated to it.

You are never dedicated to something you have complete confidence in. No one is fanatically shouting that the sun is going to rise tomorrow. They know it's going to rise tomorrow. When people are fanatically dedicated to political or religious faiths or any other kinds of dogmas or goals, it's always because these dogmas or goals are in doubt.

—Robert Pirsig, Zen and the Art of Motorcycle Maintenance, p. 152