Chapter Summary. The second book of the Posterior Analytics is a sustained investigation of different modes of inquiry aimed at achieving scientific knowledge. So understood, it has far more unity than is typically claimed for it, and its last chapter is a fitting conclusion. But it does not present, let alone defend, substantive norms to guide distinct scientific inquiries. Those norms are domain-specific and as such are presented and defended in the introductions to Aristotle’s scientific treatises themselves. What, then, is accomplished by APo. ii? In this chapter, I introduce and defend the idea that APo. ii provides an erotetic framework for any inquiry, provided only that its goal is epistêmê, demonstrative knowledge. As such, it can be thought of as providing metalevel norms, for example, about how different inquiries ought to be staged, or about how inquiries aimed at formulating definitions are related to those aimed at achieving causal demonstrations.