Aristotle, a disciple of Plato, was a creative thinker in fields as varied as ethics, logic, psychology, poetry, and politics, and he founded comparative anatomy. Aristotle, however, erroneously believed the heart to be the source of all mental processes. He reasoned that because the heart is warm and active, it is the locus of the soul. Aristotle argued that because the brain is bloodless, it functions as a “radiator,” cooling hot blood that ascends from the heart. The influence of Aristotle’s so-called cardiac hypothesis proposing the heart as the seat of such emotions as love and anger can still be seen in words such as heartbroken. Nevertheless, Aristotle’s view of nature and his anatomic findings dominated medical thinking and methods for the next 500 years.