For the debut of his latest weighty title, “On War in Philosophy,” the French philosopher Bernard-Henri Lévy made the glossy spreads of French magazines with his trademark panache: crisp, unbuttoned white Charvet shirts, golden tan and a windswept silvery mane of hair. But this glamorous literary campaign was suddenly marred by an absolute philosophical truth: Mr. Lévy backed up the book’s theories by citing the thought of a fake philosopher. In fact, the sham philosopher has never been a secret, and even has his own Wikipedia entry. In the uproar that followed over the rigors of his research, Mr. Lévy...