Each Problem That I Solved Became

From Part II of the Discourse on the Method (1637), in René Descartes's account of how he generalised his mathematical method to all domains of inquiry. When he solved a geometrical problem, the technique used in the solution became a reusable tool for subsequent problems of the same type. He saw this as the model for all scientific progress: individual solutions accumulate into a body of method that grows cumulatively in power. Gottfried Wilhelm Leibniz, who read Descartes closely, extended this vision into his project for a universal calculus of reasoning.