Discourse on the Method

A short work in six parts, published anonymously in French in 1637 as the preface to three scientific essays on optics, meteorology and geometry. Part autobiography, it opens with the remark that good sense is the most evenly shared thing in the world. Part 1 tells how Descartes found his schooling uncertain and turned to the 'book of the world'. Part 2 recalls a winter day in a stove-heated room and gives four rules of method: accept only what is clear and distinct, divide problems, proceed from simple to complex, and review everything. Part 3 sets out a provisional morality to live by while doubting. Part 4 sketches the metaphysics later developed in the Meditations: radical doubt, 'I think, therefore I am', the existence of God, and the distinctness of mind from body. Part 5 summarises his physics and the circulation of the blood and argues that animals are machines, while language and flexible reason mark the human mind. Part 6 explains why he publishes.

It is the most readable introduction to Descartes and to the modern ideal of method, and it contains the first published statement of the cogito.