Plato is known to have given only one public lecture, called "On the Good." We have one highly reliable quotation from Plato himself, stating his doctrine that "the Good is one." The lecture was a set of ideas that existed as an historical event but is now lost--and it dealt with ideas of supreme importance, in brief form, by the greatest of philosophers. Any reading of the lecture is speculative. My approach is philosophical rather than historiographic. The liminal existence of (...) the lecture is taken as an exemplar of the retrieval of what is lost in historical time. Through the lecture-event I examine several major schools of Platonic interpretation--the esotercists of the 1950's, and after, and Hans-Georg Gadamer and the "aporetic" reading--and reject most of it. My method is to establish in tandem an explanation of the lecture doctrine, especially by a reading of issue of normative ethics in the Philebus, and an account of how we are to understand Plato's way of teaching. Plato affirms the existence of the Good itself and was concerned with explaining its relation to persons as moral agents, which includes teaching, amidst the determinants of moral life and in transmission across time. The tension between universal good and plural goods suggests a fruitful relationship between normative ethics and historical theory. I apply this especially to the viability of intellectual history, to material culture studies, and to our understanding of the way in which history "lives." For this I suggest "a moral turn" in historiography in support of cultural theory. (shrink)