Discourse on the Method

Full text.
One of the most influential works in the history of modern philosophy, and important to the development of natural sciences.
In this work, Descartes tackles the problem of skepticism, which had previously been studied by Sextus Empiricus, Al-Ghazali and Michel de Montaigne. Descartes modified it to account for a truth he found to be incontrovertible. Descartes started his line of reasoning by doubting everything, so as to assess the world from a fresh perspective, clear of any preconceived notions.