In this chapter, I take up a question which follows from the issues discussed in the previous ones. I have considered ways in which Greek thought, both as expressed in poetry and philosophy, assumes that there are objective norms, in psychology, ethics, and politics. This gives rise to the question: what is the ultimate basis for these norms? I focus on one kind of answer to this question, and on the debate from which this answer arises. This answer is that the normative basis for psychological, ethical, and political life exists in ‘nature’, in some sense. Versions of this answer can be found in, for instance, Plato, Aristotle, the Stoics and Epicureans; and their answers build on fifth-century controversy about the relationship between ethics and nature, as well as developing an important feature of Presocratic thinking.