 Despite their enthusiastic reception of Aristotle’s works, the medieval moralists did not grant him complete authority in moral reasoning. The flexibility of Aristotle’s ethics, which Thomas himself acknowledges, did not lead medieval writers to construct a moral theory which, like Aristotle’s, is based on societal norms, tradition and human actions. The medieval moralists sought a more secure foundation for determining ethical action than Aristotle’s appeal to the man of practical wisdom (phronimos). A modern author recognizes the tensions that exist in medieval ethical theory when he writes of Thomas Aquinas: ‘How is it that Aquinas can seem so Aristotelian in his description of human action and yet be so Augustinian in his insistence on the need for conformity to the eternal law?’ (Westberg, 34). The answer to this question lies the account of the genesis of the human moral act and the conditions for its rectitude. Practical reason requires a foundation more secure than the accepted practice of human actions. In the search for that basis, Thomas and his contemporaries construct a theory of practical reason far more complex than the mere designation of a type of intellectual reasoning; it becomes an account of the nature of moral goodness itself.