Plato and Aristotle each present traditional forms of religious practice (e.g., sacrifice, choral performance, prayer, and temple cult) as activities that are worth performing. Because these philosophers advocated such unconventional theological views, their endorsement of conventional religious practice strikes some readers as surprising. This dissertation examines why Plato and Aristotle defended traditional religious practice. Specifically, it investigates their views on its efficacy (i.e., what benefits religious practice produces and how it is thought to produce them). Chapters 1-2 provide the intellectual (...) background necessary to appreciate Plato and Aristotle’s individual contributions. Chapter 1 outlines a view of efficacy that was common in the archaic period (the “Traditional View”). It shows that the literature from that period consistently promoted the idea that, through the performance of traditional religious practice, humans can influence the gods to effect change in all spheres of life: in the cosmos, the city, and the individual psyche. Chapter 2 shows that this view was destabilized in the dawn of the classical period, in the fifth century BCE. The pre-Socratic philosophers and Sophists of this period introduced several theological innovations that forced their proponents to reevaluate the traditional story about what traditional Greek religious practices accomplished and how they accomplished it. Plato both expands and narrows the understanding of efficacy that is set forth in the archaic age. He argues that, for a token religious practice to be successful, it must be performed according to certain ethical standards. Chapter 3 outlines Plato’s ethical criteria and argues that, while the philosopher, like proponents of the Traditional View, denies the efficacy of “illegitimate” performances that contravene these standards, he believes that religious practice can influence all realms of human life theogenically through the instrumentality of the gods. It also shows that Plato expands the modes of efficacy by introducing the possibility that religious practices produce benefits anthropogenically, without the assistance of the gods. Chapters 4-5 each detail a specific religious practice and articulate how Plato thought they could be executed according to his standards. Chapter 4 investigates Plato’s identification of choral performance and sacrifice as forms of play in the Laws, arguing that he imagined them to function as games do elsewhere in that work, when pursued in accordance with the laws and reason, and when performed for pleasure’s sake. Chapter 5 evaluates the role of petitionary prayer in Plato’s dialogues and shows that the philosopher valued the practice for its ability to facilitate intellectual achievement and integrated petitionary prayer into his psychology. Chapters 6-7 focus on Aristotle’s treatment of efficacy. Chapter 6 examines Aristotle’s Metaphysics Λ and argues that, in contrast to Plato, Aristotle discards the Traditional View entirely by denying the ability of religious practices to move the gods to action or to effect change in the cosmos. It reconciles passages from the Nicomachean Ethics and Politics, which seem prima facie to endorse conventional attitudes towards the gods, with the philosopher’s metaphysical views, which appear to contradict them. Chapter 7 examines the social and psychological benefits of religious practice in Aristotle’s Politics, where the philosopher claims that the institution of religion forms a necessary part of the city. It demonstrates that, for Aristotle, religious practice provides residents with rest and leisure, obligates them to observe laws, and promotes the development of friendship between residents. (shrink)