From The Virtues, Or The Examined Life
We know that Aquinas in the Summa theologiae begins his analysis of virtue with the standard textbook definition of virtue that was common among 13th-century moralists: “Virtue is a good quality of mind, by which one lives righteously, of which no one can make bad use, which God works in us without us.” Following normal procedure, we can consider each element of the definition as Aquinas explains it within his general teleological view of the moral life. First, the formal cause: “Virtue is a good quality of mind.” For Aquinas, virtue belongs to the generic category of quality; more specifically he places it within that kind of quality that Aristotle called habitus. As a philosophical notion, habitus signifies the perfection of a human capacity that enables a person not only to act, but to act well. Because the virtues really alter the particular substances in which they inhere, these good habitus modify or shape the psychological capacities of the human person. But this happens in a way that respects the virtuous person’s ability to express a full range of creativity and human initiative. New Testament belief does not produce boring uniformity; rather the Christian experiences a kind of second-nature conformity to gospel values that makes living an upright life prompt, joyful, and easy. Since virtue is supple, the virtuous person can decide and act on moral issues that result from even the most complex circumstances of the moral life.
Second, the material cause: Since virtue exemplifies a moral or spiritual reality, strictly speaking virtue has no material cause. Rather, for the purposes of analysis, we speak about the subjects in which the virtues exist as supplying for their material cause. These subjects include all the rational powers or capacities of the human soul: intellect, will (or the rational appetite), and the sense appetites. To possess human nature in itself does not suffice to cause virtue; rather, acquired virtue develops by some deliberate exercise of the human capacities or powers, viz, intellect, will, sense appetites.
Third, the efficient cause: “which God works in us without us.” While human actions can account for the development of the habitus that we call the acquired virtues, the definition envisages the infused virtues as sheer gifts of divine grace. That is, these virtuous forms come directly from the power of the Holy Spirit, who alone serves as the efficient cause of their coming to be and remaining in us. Because their origin and development depend on the divine agency, the infused moral virtues function only within the broader context of the theological life, of faith, of hope, and of charity.
Fourth, the final cause: “by which one lives righteously, of which no one can make bad use.” As an operative habitus, the end or final cause of virtue remains the performance of the virtuous action itself. By definition, the exercise of virtue results only in the embrace of good objects. Each of the moral virtues formally marks off an area of human endeavor, but without specifying the exact shape that every good choice will take. The moral goodness that the virtues realize embraces the whole universe of moral objects precisely as these conduce to our possession of the supreme object of all human pursuit and desire. From a teleological perspective, there really are no general “basic human goods,” for every virtuous act that is to be done in some way embodies a good basic or fundamental to the human flourishing of the person who acts.