Tamar Gendler, teaching Yale's Philosophy and the Science of Human Nature, surveys four historical attempts to divide the human mind into competing parts. She works through Plato's split of reason, spirit, and appetite, Hume's contrast between reason and passion, and Freud's id, ego, and superego, then turns to Jonathan Haidt's four modern divisions: mind versus body, left brain versus right brain, old brain versus new brain, and controlled versus automatic thought. The lecture closes with a close reading of a vivid passage from Plato's Phaedrus, using it to test how well ancient tripartite psychology maps onto later scientific accounts of internal conflict. Chapter markers move from an overview through each thinker in turn, giving the session a clear structure for comparing philosophical and empirical models of the divided self.