Here Densmore offers aguide book to Newton’s Prinipia. It includes a translation, with notes and extended proofs. 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, allowing students to reconstruct Newton’s propositions authentically.