To Plato we are indebted for the hypothesis, breathtaking in its boldness, that the highest object of desire, study and action is the good. In one form or another, that suggestion was accepted by many of his successors in the ancient and medieval world. Aquinas, for example, is following in his footsteps, when he says: ‘this is the first precept of law, that good is to be done and pursued, and evil is to be avoided. All other precepts of the natural law are based on this’ (Summa Theologica, Pt. I–II, Q. 94, Art. 2). The practical pre-eminence of good is not a notion that evaporated in the modern era; on the contrary, it lies at the heart of utilitarianism. However, a second cardinal doctrine of utilitarianism, namely that good can be quantified and must be increased without limit, does not play an important role in Plato or in pre-modern ethics, although we find something resembling that idea in the Protagoras. In the Philebus, however, Plato instead emphasizes the affinity between goodness and limit, form, structure, measure and other such notions. Whatever is good – knowledge and pleasure, for example – is good only up to a certain point, and no more. A good life for an individual requires some proportionality or mixture, and likewise what is good for the political community. Many modern philosophers, by contrast, suppose that rationality itself requires maximizing something; according to their way of thinking, the only appropriate stance to take towards what is good is to produce as much of it as possible.