"The work of Copernicus and Kepler is the work of men searching the universe for the harmony their commingled religious and scientific beliefs assured them must exist, and in aesthetically satisfactory mathematical form. To men who were convinced that an omnipotent being, designing a mathematical universe, would certainly prefer the superior features of the new theory, there could only be one conclusion—the heliocentric theory was true. ... There was a mystic element in their thinking that now seems anomalous in great scientists. ... But despite the presence of mystic, poetic, and religious influences, Copernicus and Kepler were thoroughly rational in rejecting any speculations or conjectures that did not agree with observations. What distinguishes their work from medieval vaporizings is not only the mathematical framework of their theories but their insistence of making the mathematics fit reality. In addition, the preference they showed for a simpler mathematical theory is a thoroughly modern scientific attitude. ...their willingness to think in terms of, and indeed their preference for, a heliocentric theory, despite the arguments ...against the reasonableness of such a view in their time, marks them as heroes in the intellectual battles man has fought to attain a secure dwelling place for science."