In his study of the quadrature and duplication-problems, Hippocrates contributed much to the geometry of the circle.
When one turns to psychological models of mental illness, one finds that the psychodynamic model of human mind and of mental disease is also of considerable antiquity. Thus, Empedocles of Agrigentum (490-430 B.C.) from whom Hippocrates took the theory of four elements, stressed the importance of emotions of love and hate as the controlling agents of human behavior and of physiological functions.
One of the greatest achievements of Plato and his school is the invention of analysis as a method of proof. To be sure, this method had been used unconsciously by Hippocrates and others; but Plato, like a true philosopher, turned the instinctive logic into a conscious, legitimate method.