Moral

Starting with the early church fathers, Christian thinkers took differing views of the proper relationship between their moral system and that of the pagan philosophers of antiquity. On the one hand, St. Ambrose (c. 340–397), in De officiis ministrorum (On the duties of the ministry), was prepared to adapt the Stoic-inspired account of virtue set out in Cicero's (106–43 B.C.E.) De officiis (On duties) to the needs of Christians seeking eternal bliss in the afterlife. On the other hand, St. Augustine (354–430), another doctor of the church, denied that Christians could learn anything from pagans about either virtue in the present life or happiness in the next, both of which were gifts of God's grace.

Ambrose's conviction that the ancient framework of ethical theory could be extended and modified to accommodate Christianity found wide resonance in thinkers from the Iberian bishop St. Martin of Braga (c. 520–580), who wrote influential moral tracts closely based on the writings of the Roman Stoic Seneca (4 B.C.E.?–65 C.E.), to the Cistercian abbot Ailred of Rievaulx (1109–1166), whose treatise De spirituali amicitia (On spiritual friendship) is modeled on Cicero's De amicitia (On friendship).

The uncompromising position of Augustine was echoed by monastic moralists such as Abbot Rupert of Deutz (c. 1076–c. 1129), who rejected pagan philosophers out of hand on the ground that they had no knowledge of spiritual or heavenly values. The first medieval philosopher to put forward a serious challenge to Augustine's characterization of virtues as gifts of divine grace was Peter Abelard (1079–1142). Drawing on Cicero and on Boethius's (c. 480–c. 524) commentary on Aristotle's (384–322 B.C.E.) Categories, he defined natural virtues as fixed dispositions that were acquired by the exercise of human powers and that could be transformed into Christian virtues by being directed toward God. Abelard was nevertheless acutely aware that while Seneca, the pagan philosopher he most admired, held that virtue must be sought for its own sake, Christians believed that virtue should be pursued in the hope of a greater reward: happiness in the future life.

It was precisely this issue that made Aristotelian ethics, with its this-worldly orientation, particularly problematic for medieval Christians. In the Nicomachean Ethics, which began to be available in Latin translation at the end of the twelfth century, Aristotle declared that humankind's supreme good was a happiness that consisted of philosophical contemplation in the present life—a view that was clearly incompatible with the Christian belief that humanity's highest and ultimate goal was everlasting bliss in the afterlife. A solution to the problem was found in the mid-thirteenth century by scholastic philosophers at the University of Paris. Building on a distinction originally made by the French theologian William of Auxerre (d. 1231), they maintained that the subject of Aristotle's treatise was imperfect happiness, a natural state attainable in the present life by human powers, while perfect happiness or beatitude, a supernatural state attainable in the next life through grace, was the subject of theological, not philosophical, inquiry.

This position was further developed by the Dominican theologian and philosopher Thomas Aquinas (c. 1225–1274), who carved out a legitimate area of investigation for moral philosophy: the examination of the limited happiness that can be achieved by man through the naturally acquired virtues described by Aristotle, whereas theology was concerned with the unlimited heavenly beatitude produced by divinely infused virtues. This formulation, which established that Aristotelian moral philosophy, though vastly inferior to Christian theology, was nonetheless fundamentally in agreement with it, made it possible for university professors from the late Middle Ages to the end of the Renaissance and beyond to base the teaching of ethics firmly on the doctrines of Aristotle.