Contingencies in Nature may be explained, but such explanations refer to other contingencies (pt. I). Is there a way to "explain away" all contingencies? The first physical theory of modern times, Newton's theory of gravitation, was received in a way that leaves this question open (pt. II), while Kepler's theory of cosmological harmony arrived at a positive solution (pt. III). However, later developments in science outdated Kepler's approach (pt. IV).