Makes the great adventure of Principia available not only to modern scholars of history of science, but also to nonspecialist undergraduate students of humanities. It moves carefully from Newton's definitions and axioms through the essential propositions, as Newton himself identified them, to the establishment of universal gravitation and elliptical orbits. The guidebook unfolds what is implicit in Newton's words as he himself would have filled in the steps and completes the argument in ways that are authentic and not anachronistic, exactly following Newton's thinking rather than substituting tools of modern calculus or the formulations of modern physics. It is Newton in his own terms. This is a wonderful book. —Richard S. Westfall