A.N. Whitehead famously remarked that “[t]he safest general characterization of the European philosophical tradition is that it consists of a series of footnotes to Plato.” While this is of course an overstatement, it cannot be denied that Plato considered just about every philosophical topic and wrestled with just about every philosophical question in the course of his staggering career. We will examine the philosophical tradition that Plato inherited, including the thought of the pre-Socratics, the so-called sophists, and Plato’s teacher Socrates, and consider how it was transformed by Plato, covering themes from across Plato’s metaphysics, epistemology, ethical philosophy, political philosophy, philosophy of mind, and philosophy of science.