He first threw out his senses because he couldn't trust them. He stated that they can deceive, but to be deceived he must exist. Therefore, Descartes concludes that the only way to prove one's existence is through thought. Descartes wrote “thought, this alone is inseparable from me, I am, I exist. - this is certain” and should no longer exist once it stops thinking (page 18 p 27.) According to Descartes, to exist and be certain of our existence we must be something that “doubts, understands, affirms, denies, is willing , is not willing, imagines and has sensory perceptions” ultimately we must be intellectual and not flow through the movement of our deception