The form of the Good in Plato’s Phaedo and Republic seems, by our standards, to do too much: it is presented as the metaphysical princi­ple, the epistemological principle and the principle of ethics. Yet this seemingly chimerical object makes good sense in the broader context of Plato’s philosophical project. He sought certain knowledge of neces­sary truths (in sharp contrast to the contingent truth of modern science). Thus, to be knowable the cosmos must be informed by timeless princi­ples; and this leads (...) to teleology and the Good. The form of the Good, it is argued, is what makes the world knowable insofar as it is knowable. This interpretation plugs a significant gap in the scholarship on the Good and draws attention to a deep connection between Plato’s episte­mology and his teleological understanding of the cosmos. (shrink)