In 1789 James Madison and Thomas Jefferson engaged in one of their many exchanges on constitutionalism. As with other Jeffersonian flights of philosophy, the younger Madison had to rein in the excesses of his senior partner and collaborator. The issue at hand was Jefferson's famous opinion “that the earth belongs in usufruct to the living.” So confident was Jefferson in the truth of this idea that he called it “self-evident.” Their exchange has received insightful and comprehensive analysis, which needs no revisiting here. Adrienne Koch, whose treatment of this “intellectual reciprocity” is among our most careful, sees it as revealing the essence of the two men, pitting the “more speculative and more daring” Jefferson against “the more astute politician” Madison.