Discourse On The Method Part V

Overview

Descartes now moves from metaphysics to natural philosophy. He asserts that there are natural laws instilled into us and the world by God, and these laws cannot fail to be observed. They govern everything.

He then surveys his findings across various domains, particularly astronomy and physics. He discusses the sun, fire, the moon's effect on waves, water flow, and more. His goal is to explain these phenomena so thoroughly that no questions remain.

He turns next to biology. Human bodies, he notes, are similar to those of animals. He examines the heart, its arteries, blood flow, how the brain functions, and what changes occur in it when we grow tired. The mechanical workings of the body can be understood through observation and reason.

But then what distinguishes man from beast? Descartes identifies two key differences. First, man speaks; beasts do not. Second, man acts through reason and thought, while beasts act purely through nature and instinct. A parrot might mimic words, but it does not understand them. An animal might perform complex behaviors, but these arise from disposition, not deliberation.

This leads Descartes to his conclusion about the soul. The soul is not derived from matter. It is not the body. It is a separate entity that joins with the body but remains distinct from it. This is what makes us more than mere machines.