1. The coolest philosopher ever. In his book "Meditations," he states that perhaps the entire world is merely an illusion that some decieving demon put into his mind. This idea led to some awesome movies, such as The Matrix and The Truman Show.
2. A dualist, which means that he believes that the mind and the body are seperate entities. He's a wise man, this Descartes.
Descartes thinks, therefore he is.