Rationality in Ancient Stoic Psychology

Abstract

My dissertation offers a new interpretation of the psychological theory of the ancient Stoic philosophers, in particular of their account of what it means to be rational. According to the interpretation proposed here, the Stoics conceive of rationality, in its most fundamental sense, as a capacity to receive certain kinds of information: more specifically, to be rational is to grasp information which has conceptual and language-like structure. In propounding this doctrine, the Stoics say more than the commonplace that it is possible to assign propositional content to the mental states of adult humans. Rather, they mean to advance a more ambitious claim regarding the features which set apart rational cognition from the kind of thinking engaged in by young children and non-human animals. According to the interpretation defended here -- reconstructed on the basis of the relatively few surviving Greek and Latin fragments which record ancient Stoic doctrine -- only rational minds correlate each sense-impression (phantasia) with a single sentential entity, or 'sayable' (lekton), which suffices to express all of what the impression sensorily represents. And since the Stoics claim that all of our beliefs, intentions to act, and emotions are just acts of 'assent' (sunkatathesis) to the content of our sense-impressions, they can defensibly posit this correlational capacity as the fundamental feature of adult human psychology, governing all of its activities. My dissertation aims to present this account of rationality in detail and to explore how it illuminates further aspects of Stoic doctrine in the domains of ethics, action theory, and epistemology.