In particular, he made a distinction between the soul and the spirit, and he developed his own theory on the soul. He also crtiticized the ideas of Avicenna and Aristotle on the soul originating from the heart. Ibn al-Nafis rejected this idea and instead argued that the soul “is related to the entirety and not to one or a few organs.” He further criticized Aristotle’s idea that every unique soul requires the existence of a unique source, in this case the heart. Ibn al-Nafis concluded that “the soul is related primarily neither to the spirit nor to any organ, but rather to the entire matter whose temperament is prepared to receive that soul” and he defined the soul as nothing other than “what a human indicates by saying ‘I’.”[40]

He also identified the “psychic faculties” with cognition, sensation, imagination, and animal locomotion,[41] and disproved Aristotle’s notion that these come from the heart rather than the brain. After Ibn al-Nafis discovered that the brain and nerves are cooler than the heart and arteries, he argued that the psychic faculties come from the brain on this basis.[42] He further wrote that it is the brain which controls sensation, movement and cognition.[43]

http://en.wikipedia.org/wiki/Ibn_Nafis