 What role does experiment play in Cartesian science? In The World and Principles II, Descartes deduces the principles of physics (the laws of nature) from the first principle of metaphysics: God. The laws of nature can be deduced by reason alone from God’s immutability (see AT 11: 36–48, CSM 1: 92–98; AT 8A: 61­67, CSM 1: 240–244). Experiment plays no role in Descartes’ deduction of the laws of nature. However, this does not mean that experiment plays no role in Cartesian science. On the contrary, in Discourse VI, Descartes clearly indicates when experiments become necessary in the course of scientific inquiry: