On his famous walk to Vincennes to visit the imprisoned Diderot, Rousseau had what he called an "illumination"--the realization that man was naturally good but becomes corrupted by the influence of society--a fundamental change in Rousseau's perspective that would animate all of his subsequent works. At that moment, Rousseau "saw" something he had hitherto not seen, and he made it his mission to help his readers share that vision through an array...