This is part 1 of the recording of my talk at the Fourteenth Annual Marquette Summer Seminar on Aristotle and the Aristotelian Tradition, "The Significance of Thumos in Platonic and Aristotelian Moral Psychology". An important difference between the Platonist tradition and the Aristotelian is the status accorded to thumos in their respective moral psychologies. In very broad strokes, the Platonic tradition consistently follows and reinterprets Plato’s tripartite conception of the soul, maintaining thumos one of three main parts of the soul, distinct from, in between, and interacting a rational part and the appetites. Thumos has a clear scope and proper function in Plato’s texts and those of later Platonists. In Aristotle’s moral psychology, thumos has a more restricted status, for the most part reinterpreted as one main mode of desire or affectivity (orexis). By contrast to other moral psychologies, e.g. that of the Stoics who treat thumos as just one emotion or passion among others, thumos in Aristotle and the Aristotelian tradition retains a distinctiveness from other, lower forms of affectivity, evidenced by discussions like that of akrasia due to thumos in N.E. 7 or that of thumos as one of the main causes for human actions in Rhet. 1. The status, function, and proper education of thumos remained a matter of contention and reinterpretation through antiquity, evidenced by discussions bearing upon thumos, for example in Plutarch, Galen, Philo, among others. My paper first outlines Plato’s treatment of thumos, drawing primarily upon Republic and Timaeus. It then sets out an Aristotelian account of thumos reinterpreted as a main mode of orexis, central to anger (orge), friendship, and other affective states, drawing mainly upon the two Ethics, the Politics, and the Rhetoric. Similarities and continuities between Plato’s and Aristotle’s positions are stressed, particularly the need to understand, orient, and educate thumos. Both positions are briefly contrasted against other interpretations which do not accord thumos a distinctive status, including Stoic thought. The paper also briefly discusses selected later reinterpretations of and controversies about thumos in the ongoing Platonic and Aristotelian traditions. To support my ongoing work, go to my Patreon site - www.patreon.com/sadler If you'd like to make a direct contribution, you can do so here - www.paypal.me/ReasonIO - or at BuyMeACoffee - www.buymeacoffee.com/A4quYdWoM You can find over 3500 philosophy videos in my main YouTube channel - www.youtube.com/user/gbisadler