Plato famously promised to complement the Sophist and the Statesman with another work on a third sort of expert, the philosopher--but we do not have this final dialogue. Mary Louise Gill argues that Plato promised the Philosopher, but did not write it, in order to stimulate his audience and encourage his readers to work out, for themselves, the portrait it would have contained. The Sophist and Statesman are themselves members of a larger series starting...