Divide Each Difficulty Into As Many

From Part II of the Discourse on the Method (1637), this is René Descartes's second rule of method, the rule of analysis. The four rules together constitute his alternative to the scholastic logic he was taught at La Flèche: never accept anything as true unless it is clear and distinct; divide problems into manageable parts; proceed from simple to complex; review to ensure nothing is omitted. The second rule — decomposition — anticipates the modern engineering and scientific practice of breaking complex problems into independently solvable subproblems.