EXCERPT Kant began something quite new in the history of Western philosophy, by adapting thought to a rigorous austerity. Unlike Descartes, for whom doubt was only a detour to a more secure edifice of knowledge, Kant committed his thought to renunciation. Following Luther, he steeled himself against the seductions of ‘the whore of reason’, pursuing an ascetic doctrine that he baptized ‘critical philosophy’. His great temptation was to write a ‘system of pure reason’—the constructive philosophy that Hegel accomplished in his Logic—but he did not succumb, and went to his grave with his speculative virginity intact…