Thesis advisor: James F. Keenan / This dissertation aims to give a theoretical account of the cardinal virtue of temperance that portrays it as an attractive (albeit demanding) virtue, and provides the justification and method for applying it to multiple spheres of life today. To this end, it offers a critical interpretation and retrieval of Saint Thomas Aquinas' account of the four causes of <italic>temperantia<italic> in the <italic>Summa Theologiae<italic>. I claim that, for Thomas, the four causes of a moral virtue are its mode (formal cause), matter and subject (material cause), proper end (final cause) and agent (efficient cause). Less technically, they can be expressed in terms of five guiding questions to be used in understanding any given virtue: What is the practical wisdom actualized by that virtue? What is the sphere of life with which the virtue is concerned? What aspect of the human heart and mind does the virtue modify? What is the virtue for? What causes the virtue to exist and increase? To answer to these five questions is to give an account of a moral virtue. This dissertation develops and applies this causal method for analyzing a moral virtue, both as a means of interpreting Thomas' account of temperance, and as a tool for constructing a theory of temperance for today. Temperance, I claim, can be defined as the modulation of attraction for the sake of right relationship. It is developed through both discipline and grace. Temperance does not repress desire, but forms and channels its positively, placing it at the service of right relationship to oneself, others, the earth and God. It does limit and restrain desire, but always for the sake of deeper and more meaningful goods. Temperance therefore modulates harmoniously between the restraint and the redirection of desire, the fast and the feast. Temperance is often misunderstood as proposing a purely negative ideal of repression and constraint. The dissertation claims that, on the contrary, temperance is a positive and attractive virtue, and one that is urgently needed in consumer society. / Thesis (PhD) — Boston College, 2010. / Submitted to: Boston College. Graduate School of Arts and Sciences. / Discipline: Theology.