When it appeared in 1670, Baruch Spinoza's Theological-Political Treatise was denounced as the most dangerous book ever published--"godless," "full of abominations," "a book forged in hell . . . by the devil himself." Religious and secular authorities saw it as a threat to faith, social and political harmony, and everyday morality, and its author was almost universally regarded as a religious subversive and political radical who sought to spread atheism throughout Europe. Yet Spinoza's book has contributed as much as the Declaration of Independence or Thomas Paine's Common...