This contribution aims to promote a dialogue between history and psychology by outlining a direction for future research at the intersection of these disciplines. In particular, it seeks to demonstrate the potential contributions of history to psychology by employing the category of mental health in a historical context. The analysis focuses on notions of psychological health that were developed in late antiquity, especially the equation between "health of the soul" and dispassion (apatheia) within the Christian monastic movement. This theologically informed notion of what constitutes positive human functioning and well-being is examined in view of modern attempts, in mainstream and positive psychology, to define mental health. The optimism concerning the naturalness of virtue and the malleability of human nature that underlies late antique notions of "health of the soul" becomes noticeable in its absence once we turn to modern notions of mental health. It thus provides an illuminating counter-example against which to compare and analyze modern attempts to define mental health. A comparison of these alternative notions human flourishing offers an opportunity to reflect on and test the validity of contemporary attempts to define this condition in a culturally sensitive manner.