In the preface to the second edition of the Critique of Pure Reason, dated April 1787, Immanuel Kant names the philosopher Christian Wolff as the originator of der Geist der Gründlichkeit in Deutschland, the spirit of thoroughness in Germany. Wolff showed, Kant writes, how a science should proceed. It needs principles established by rule, clear definitions of concepts, rigorous proofs, and no bold leaps in its conclusions. Kant adds that this spirit had not died in Germany. It had only been shouted down for a short time by a fashion for genius-style freedom of thought.