The 1st-century writer known as Longinus not only delineated the true nature of "sublimity" but set down rules for achieving it. We analyze his approach to theory and his influential conception of the ideal audience for sublime literature. Finally, we watch with awe as Longinus mounts a direct refutation of Plato's Republic that not only converts Plato's negatives into positives, but recasts Plato himself as one of the most sublime poets ever.