ABSTRACT Focused upon Descartes’ writings and letters, this paper considers the exponentially-charged relationship between sadness, melancholy, doubt and philosophical inquiry. The first sections examine the relation between sadness in the Cartesian corpus and melancholy as a traditional pathological classification, with both set against a larger seventeenth century intellectual discourse. The letters exchanged between the Princess Elisabeth of Bohemia and the Palatine and Descartes between 1643 and 1649, that is, just prior to the death of the philosopher in 1650, reveal the (...) central paradigm of this particular relationship between sadness and melancholy. The call to use philosophy as a cure against sadness also enters consideration, with the theatrical, artificial nature of the philosophical cure presented as essential not only to Descartes’ relation to sadness, but also to philosophical method in general. The moral aspect of the establishment of mental habits and their emendation by philosophy hence yields central insights into the larger Cartesian project, here viewed as essentially premised upon a medical vocation. (shrink)