Towards the end of the 1500s a French philosopher and mathematician by the name of René Descartes was born. He was the most well known figure in cognitive neuropsychology at this time. Some of Descartes’ contributions stemmed from his interest in the nervous system and brain’s role in behavior. He posited that the nervous system was made up of hollow tubes which filled with “animal spirits” any time an action were to take place in that part of the body. His other contributions included the more developed notion of dualism. He hypothesized that the brain and mind are two separate entities that exist on their own but are interdependent on each other. He theorized that the pineal gland in the brain is where these two separate entities interacted. Descartes’ dualistic theory serves as his most influential contribution to cognitive neuropsychology.