The Conclusion to the Practical Syllogism: A Comparison of the Aristotelian-Thomistic and Contemporary Analytic Traditions

The practical syllogism, classically considered to be the dominant model of practical reasoning, has fallen out of favor in contemporary academic moral philosophy. Not only is it rarely mentioned, but the practical syllogism typically considered in the contemporary literature is very different from the classical conception of the practical reasoning. In particular, whereas classical constructions of the practical syllogism as rooted in the Aristotelian tradition insist that action is the conclusion to the practical syllogism, contemporary constructions hold that the conclusion must be a proposition.

I argue that this shift in conceptions about the conclusion to the practical syllogism is due to a broader shift in dominant theories of practical reasoning. The action-as-conclusion thesis is at home in the classical, Aristotelian-Thomistic picture of practical reasoning. However, this thesis is denied plausibility in contemporary academic moral philosophy that is dominated by a Humean instrumentalist theory of practical reasoning. In this dissertation, I write about these two competing theories of practical reasoning to show how the Aristotelian-Thomistic theory of practical reasoning provides the proper background for the action-as-conclusion thesis and why the Humean instrumentalist theory makes the action-as-conclusion thesis seem ridiculous.

At the heart of this dissertation, then, is an in-depth study of St. Thomas Aquinas's theory of practical reasoning, which shows how the faculties of will and intellect co-operate in the act of practical reasoning and are both causes of action (will as efficient cause, intellect as formal cause). The premises of the practical syllogism should then be construed as expressing the role of the intellect in reasoning toward action. As the act of the intellect formally causes human action, the premises of the practical syllogism thereby 'conclude' in an action.

This dissertation concludes by showing how the picture of Thomistic practical reasoning as advanced in this dissertation is similar to and different from the projects of other contemporary Thomists. In particular, I locate this picture of practical reasoning with reference to Candace Vogler's Reasonably Vicious, Philippa Foot's Natural Goodness, and Elizabeth Anscombe's 'corrupt minds' thesis in Modern Moral Philosophy.