Renné Descartes...

He brought up the mind-body problem: the mind is essentially a thinking thing, while the body is essentially an extended thing - something which occupies space. Descartes held that there is two way causal interaction between these two quite different kinds of substances. So, the body effects the mind in perception, and the mind effects the body in action. 

His system is known as methodic doubt: We have to assume that everything we know is false; we have to start from 0 to achieve knowledge.

He believed that everything is made up of reason and matter. He proved the existence of reason by saying: “I think therefore I exist” and the way to prove the existence of the matter is through the existence of God. (God exists because I can think of him and he exists because he wouldn’t be so mean to let me think of him if he wouldn’t exist)

As we are part of God.. if he exists everything exists , everything is truth. 

CARTESIAN PARADOX