If Kepler’s evolution had stopped here, he would have remained a crank. But I have already pointed out the contrast between the a priori deductions in the first part of the book and the modern scientific approach of the second. This co-existence of the mystical and the empirical, of wild flights of thought and dogged, painstaking research, remained, as we shall see, the main characteristic of Kepler from his early youth to his old age.
