⇒ Descartes believed that he could prove his experience using logical reasoning alone

⇒ Essentially his idea was that if you can follow his method of systematic doubt - which involves doubting everything you learn from experience or your senses - then you must exist. Because you can't doubt or question your own existence unless something exists to do the doubting or questioning.

• Also see this Wikipedia article on Cartesian doubt if you want to read more on this topic

⇒ Not only did Descartes claim he could prove your own existence, but he also claimed he could prove the existence of God using logic/reasoning

⇒ His ontological argument for the existence of God, for example, went like this:

1. Our idea of God is of a perfect being
2. It's more perfect to exist than not to exist
3. Therefore, God must exist

Previous notes: Introduction to the theory of knowledge

Next notes: Innate Knowledge

Further notes:

• Knowledge as a Deductive System
• Contrasts with Empiricism