Anna Karenina by the great Russian writer Leo Tolstoy is one of my favorite novels. In his introduction to the novel Malcolm Cowley writes about Tolstoy: "Genius is energy -- mental energy first of all, but sometimes this is combined, as in Tolstoy's case, with physical, emotional, and sexual energy. Genius is vision, often involving the gift of finding patterns where others see nothing but a chance collection of objects. Genius is a memory for essential details. Genius is 'the transcendent capacity for taking trouble,' as Carlyle said; it is the capacity for brooding over a subject until it reveals its full potentialities; but that again is a form of energy. Genius is also a belief in oneself and the importance of one's mission, without which the energy is dissipated in hesitations and inner conflicts."
What's interesting is that these same characteristics also apply to many crackpots: not giving up when most normal people see the futility of the endeavor; seeing patterns in random objects when there is in fact no pattern at all; a memory of details that has devolved into attaching a nonexistent meaning to trivial events; brooding on a subject in situations where the normal individual would abandon brooding and embark on fruitful action; and a grandiose belief in the importance of one's mission -- a mission that amounts to no more than building a bridge to nowhere.