As the sixteenth Century drew to a close, the human race teetered at the brink of an unprecedented intellectual revolution. The Aristotelean conception of a small, spherical, Earth-centered cosmos ceased to confine the imagination of an increasing number of thinkers; the recently proposed Copernican system, problematic though it was, sketched a provocative alternative with some real explanatory advantages (e.g., its uniform explanation of the existence, amount, and timing of retrograde motions); and distinct intellectual currents converged in the growing search for a new dynamics that would encompass at once all motion, superlunary and sublunary. In the event, the cosmology, the planetary astronomy, and the dynamics finally came together in Newton's uniquely coherent synthesis, and by the dawn of the eighteenth century we had exchanged the dubious comfort of Aristotle's enveloping egg for the more chilling contemplation of a spatially infinite universe.