Why is logic needed as part of philosophy? This topic has always been controversial. We need logic to make sure that our arguments are sound. In ancient philosophy, logic has the function of sustaining philosophical truths and demolishing philosophical mistakes. ‘Logic and reality’ focuses on one particular metaphysical debate, whether there are purposes in nature or not, and if so what they are. The study of nature, or ‘physics’ in the ancient sense, covered more than science. It corresponded to what we call metaphysics. What is it to have a nature? What is the purpose of nature? Can the world be thought of as designed?