This chapter defends Peirce’s conception of science against a pair of current, mutually antagonistic ideas of the difference of modern science from classical and medieval philosophy. The one party celebrates the difference, the other deplores it, but they agree that modern science rejects the classical ideal of theory as knowledge good for itself. Peirce saw that difference more subtly as one in which the classical ideal of knowing is transformed rather than abandoned. This revolution in cognitive aim did not occur arbitrarily. Well-established facts about the defeat of the Aristotelian world-view are cited to support the novel thesis that it depended on an empirical yet normative discovery, that restless, unending, specialist inquiry is more satisfying intellectually than is the dialectic of systems. The history of science reviewed in this chapter provides evidence for the argument of Chapter 9, that there is normative knowledge and that it is empirical.