Rejects the theory that mental states are separable from physical states.

He believed that man has different constructs of personality that interacts with each other and along with his concept of the different levels of consciousness provides an idea how a person develops a sense of self.

According to him, consciousness is the central feature of the self.

According to him, true wisdom is knowing that you know nothing.

According to him, human behavior flow from three sources:desire, emotion and knowledge

According to him, The best way to gain knowledge was through “natural philosophy,” which is what we would now call science.

He is known for the statement “Cogito Ergo Sum” which means in English as “I think therefore I am”.

His work on the self is most represented by the concept “Tabula Rasa” which means a Blank Slate.

He believes that our notion of ourselves and our idea of existence comes from a higher form of sense in which bodily senses may not perceive or understand, and the more one doubts and question his life means that, that person is actually living.