Answer and Explanation:
Aristotle believed in contrast to his mentor and teacher Plato that the heart was the source of mental processes while the brain functioned only as a radiator that served as a means of cooling the warm heart and that more rational beings needed larger brains to cool their heart. This was against the belief of Plato that the brain was the source of all mental processes. The heart theory was dispelled by Galen, a physician during the Roman Empire.
