Discourse on the Method
Descartes describes his personal intellectual journey from disillusionment with received learning to the discovery of a four-rule method for reasoning clearly and finding truth. He applies this method to establish foundational certainties, including the famous 'I think, therefore I am,' proofs for the existence of God and the soul, and a mechanical account of the human body. The work closes with his reasons for publishing selectively and his commitment to advancing natural science, especially medicine, for the benefit of humanity.