Discourse on the Method
Rene Descartes

A cornerstone of modern philosophy, Descartes’ Discourse on the Method of Rightly Conducting One’s Reason and of Seeking Truth roots itself in the importance of skepticism to the pursuit of knowledge, the attempt to doubt everything, question everything, presume nothing at the outset of scientific or philosophical investigation. The book applies this method to a couple of different cases, most notably the existence of God, the physics of nature, and the functioning of the body, but it is not his insights into any of these but rather his fundamental premise that has proved of such lasting significance. Thus while the work’s most famous line – “I think, therefore I am” – comes from a hugely problematic reflection on the existence of God, it is a less-remembered premise that underpins the book, and indeed is considered by many to provide the cornerstone for all philosophy since: “[To] never to accept anything for true which I did not clearly know to be such”.

Discourse extends the principle of scientific inquiry based on doubt, logic and proof to the question of philosophy and general knowledge. In place of initial hypotheses, which depend themselves upon assumption, it is only logic, the careful application of human thought, which can ultimately be relied upon in learning. It is only the rational human mind that can surpass all received wisdom and can make reliable observations of the physical senses. It is no small contribution. With Descartes, European philosophy breaks with the near-hegemony of Aristotle which had previously held sway. With Descartes, we begin to enter what is called the Age of Enlightenment. With Descartes, the world changes.