Pierre-Jean Georges Cabanis was, with Comte Antoine Louis Claude Destutt de Tracy, the leader of the Idéologues. A precocious student of philosophy and of the classics, he chose medicine as a career, but he never practiced. As a protégé of Claude-Adrien Helvétius's widow, he frequented the company of Étienne Bonnot de Condillac, Baron d'Holbach, Benjamin Franklin, and Thomas Jefferson. When Voltaire disparaged his poetry in 1778, Cabanis turned to physiology and philosophy. During the Revolution, he collaborated with Mirabeau on public education and was an intimate of Marquis de Condorcet. Later, he backed the Directory and Napoleon Bonaparte's coup d'état of 18 Brumaire. Although Napoleon made him a senator, Cabanis opposed his tyrannical policies. Bitter and scornful, Napoleon dubbed Cabanis's group "Idéologues." Cabanis wrote on medical practice and teaching, but his fame and influence derive from one book, Rapports...