Often translated as "practical wisdom," the Greek word phronêsis derives from the verb phronein, meaning "to have understanding," or "to be wise or prudent." In its earliest uses the word is normative only in the sense that it signifies a correct cognitive grasp of some kind; only gradually does it come to be used in ethical contexts for a correct grasp of what ought to be done. For Plato and the other Socratics, phronêsis represents that aspect of our rational faculty that derives genuine knowledge about values and norms, that is, about the virtues (see especially Protagoras, Gorgias). The famous debate between the Socratics and their critics, such as the orator Isocrates, turned on the possibility of demonstrative knowledge in the sphere of virtue. Plato had attacked oratory on the grounds that its aim is not to discover what is...