Thomas Aquinas (1225-1274), an Italian Dominican friar and Catholic priest, is one of the most influential theologians in the Christian tradition--and certainty the most influential theologian of the Roman Catholic Church. By synthesizing classical Christian theology with Aristotelian philosophy, Aquinas's thought continues to have an astonishing impact on an array of disciplines. Scholarship on Aquinas is flourishing, with studies of natural law theory, action theory, the morality of the passions, feminism, political theory, etc. Yet despite the contemporary renewal of virtue ethics--a movement in Catholic and Protestant and Orthodox traditions that attempts to answer the question, "How should I live?"--to date no full-length treatment of Aquinas' theory of virtue exists. Nicholas Austin aims to fill that gap. Aquinas on Virtues offers a new and comprehensive interpretation of how Aquinas uses the four causes--formal, material, final, and efficient--to understand virtue in general, and how these causes underlie his treatment of specific virtues that make up the bulk of his ethics. In the final part of the book Austin applies the causal approach to four contested issues in contemporary virtue theory: practical wisdom; virtue and the passions; the teleology (or ultimate end) of virtue; and infused moral virtues, exploring the relation between grace and virtue.