One purpose encyclopedias serve is to assemble knowledge about the past. By what their authors select and how they treat it, they often provide a window onto the spirit of their own times. Today, they face an additional challenge, as free Web sites, such as Google and Wikipedia, are usurping the traditional place of reference books. This well-edited and attractively presented volume provides readers with significantly more thoughtful and wider-ranging information than they will easily find on the Web; students in particular would be wise to consult it. Except in its language, which is uniformly accessible and mercifully free of the jargon that plagues contemporary scholarship, this encyclopedia reflects the atmosphere and the concerns of the contemporary academic community as effectively as Diderot’s encyclopedia reflected the French Enlightenment. Whether early-twenty-first-century American political science will hold up as well as eighteenth-century French Enlightenment thought is a separate question altogether.