Book excerpt: How do the intellect and will remain free while pursuing a life of virtue? This is where the question of prudence comes in. Is the practical wisdom of the prudent man founded upon some kind of innate or acquired instinct, or does it presuppose understanding of intellectually grasped basic principles? And if those principles are presupposed, is reason necessary for applying them in any given instance, or can one solely look to the rightly formed appetites acquired by moral virtue? In answering these questions, Ryan J. Brady looks first and foremost to St. Thomas Aquinas and his ancient and modern interpreters. Brady’s way of engaging the question of the interplay between the intellect and reason is by focusing on two apparently conflicting texts of St. Thomas Aquinas, one of which says that synderesis (the habit of the first principles of the practical intellect) appoints the end to the moral virtues and another which says prudence does. The author’s conviction is that the correct way of reconciling the two texts not only establishes knowledge of the role of conscience, virtue, and natural law in the moral life but also provides insight into the profoundly complementary roles of reason and will within the context of a life of virtue.