Key points

Challenge of knowledge based on authority, sense and reason.

Key text: Discours de la méthode pour bien conduire sa raison, & chercher la verité dans les sciences (A Discourse of a Method for the Wel-guiding of Reason, and the Discovery of Truth in Sciences) (1649)

Key philosophies: Rationalism, Empiricism

Discussion

Descartes used doubt as critical tool, probing all ideas for weaknesses, and as such was an early presage of Popper's falsification.

He saw 'Human consciousness as the source of knowledge' and was particularly focussed on using reason, rationality and logic.

He ring-fenced areas of knowledge, leading to separate specialisations (which has since driven science) and thus breaking former holistic views of nature.

He separated the mind and the body, but paid due attention to religion, as Bacon, and provided reasoned existence for God. (priest Nicholas Malebranche later re-connected mind and body by saying only God could separate them).

His most famous saying: Cogito ergo sum. (I'm thinking about working on some maths :-)

See also

Rationalism, Empiricism