Commentators have long treated Aristotle's criticisms of Plato's Republic as the primary, if not only, source for understanding the differences between them on matters of politics. Likewise, commentators have denied that Book I of the Politics accords with the outline of that work provided at the conclusion of the Nicomachean Ethics. This dissertation argues that both of these commonly-held views are, in fact, quite mistaken and that correcting them will aid in our understanding of both Plato and Aristotle. More specifically, I argue that Book I of the Politics is Aristotle's critique of Plato's Eleatic Stranger, the primary philosophical figure in the Sophist and Statesman. The Eleatic articulates a view of nature which is hostile toward human life; therefore, he argues that the end of political life is primarily preservation. Aristotle, of course, rejects this and argues that the specific difference of politics is its concern with the good life, rather than mere life. These contrasting views about the end of politics lead to disagreements on many other topics' e.g., the variety of human partnerships and how they ought to be distinguished, the character and acquisition of political knowledge, the ability of the multitude to possess political knowledge, and the worth of the rule of law. The Eleatic Stranger is therefore a target of Aristotle's argument throughout the text. Reading the Politics in this light improves our understanding of Aristotle's political theory and offers new insight into the relationship between Plato and the philosophic figures that inhabit his dialogues. Moreover, it shows resemblances between the political theory of the Eleatic Stranger and that of modernity, which lends credence to neo-Aristotelian critiques of contemporary political life. However, by indicating that Aristotle's political theory is closely connected to his understanding of natural teleology, my argument raises the critical question of whether Aristotle's political philosophy can be preserved in light of scientific critiques of his natural philosophy.