Humoralism, the view that the human body is composed of a limited number of elementary fluids, is one of the most characteristic aspects of ancient medicine. The psychological dimension of humoral theory in the ancient world has thus far received a relatively small amount of scholarly attention. Medical psychology in the ancient world can only be correctly understood by relating it to psychological thought in other fields, such as ethics and rhetoric. The concept that ties these various domains together is (...) character (êthos), which involves a view of human beings focused on clearly distinguishable psychological types that can be recognized on the basis of external signs. Psychological ideas based on humoral theory remained influential well into the early modern period. Yet, in 17th-century medicine and philosophy, humoral physiology and psychology started to lose ground to other theoretical perspectives on the mind and its relation to the body. This decline of humoralist medical psychology can be related to a broader reorientation of psychological thought in which the traditional concept of character lost its central position. Instead of the focus on types and stable character traits, a perspective emerged that was primarily concerned with individuality and transient passions. (shrink)