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5. Can we be completely certain of anything?


In this chapter, we consider the Meditations on First Philosophy, by the French philosopher René Descartes.


5.1 We ask whether complete 100% certainty is achievable.

5.2 We describe Descartes’ project: achieving complete certainty.

5.3 We show that certainty is hard to achieve. The evil demon is introduced.

5.4 Descartes claimed that he could be certain that he exists, and that he is a thinking thing. We look at perhaps the most famous quote in the whole history of philosophy: “cogito, ergo sum”.

5.5 We discuss Descartes’ claim that certainty can be achieved by “vivid and clear perception”.

5.6 We present Descartes’ solution to the evil demon problem, including one of his arguments for the existence of God.

5.7 We present an objection to Descartes’ position: the notorious Cartesian circle.

5.8 We discuss Descartes’ legacy.

5.9 It is ironic that while Descartes set out to achieve certainty, he is remembered most for an argument that seems to show that there is very little of which we can be certain.