Prohairesis plays a central role in Aristotle's moral psychology. It is prohairesis that determines an action to be rational, that provides the proximate efficient or moving cause of rational action, and that better reveals one's character than the action itself. This paper will discuss Aristotle's shifted emphases when speaking of prohairesis in different ethical treatises; Aristotle's pursuit of the nature of prohairesis and his special argumentative strategy in dealing with prohairesis; the structure, i.e., the desiderative and deliberative components of prohairesis; (...) and will conclude with some remarks about the significance of prohairesis. (shrink)