Publication Date


Advisor(s) - Committee Chair

Arvin Vos, Alan Anderson, Edward Schoen

Degree Program

Department of Philosophy & Religion

Degree Type

Master of Arts


A major problem with current discussions on the moral theory of St. Thomas Aquinas is the fact that many interpreters present Thomas's thought as a natural-law morality. While natural law is an element of Thomas's moral theory, it plays a subordinate role to the virtue of prudence.

The natural law interpreters of St. Thomas's moral theory hold that (1) natural law is the dominant element, (2) natural law can be treated in isolation from Thomas's account of virtue, and (3) the principles of natural law make Thomas's moral theory abstract and deontological. These interpretations rarely consider the virtue of prudence.

Natural law, in Thomas's moral theory, makes general statements about human nature and also sets the parameters for morally good human activity. However, it fails to function adequately on the level of an agent's particular moral problems. The general precepts of natural law do not function as proximate principles of human action. But the special function of moral virtue is to provide the agent with the necessary proximate principles of human action.

Virtue is an acquired disposition of the soul that functions as a proximate principle of action. Holding a special place in Thomas's moral theory, prudence is primary among the moral virtues. It is defined as "right reason concerning things to be done." Prudence holds a middle place between he intellectual virtues and the moral virtues. It requires right thinking about moral matters, but it also requires the possession of a right appetite.

This essay includes some discussion of human nature, as ethics is subordinated to psychology. Furthermore, we must show how the human agent engages in moral activity, and this requires discussing the psychological processes involved in human action.

It is my purpose to explore the functions of natural law and virtue and to take account of the relationship between them in Thomas's moral theory. After establishing a proper understanding of Thomas's view, it will be clear that the natural-law interpreters have missed a crucial element in his ethical theory.


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