St. Thomas Aquinas Enthroned Between the Doctors of the Old and New Testaments, with Personifications of the Virtues, Sciences, and Liberal Arts, fresco by Andrea da Firenze, c. 1365; in the Spanish Chapel of the church of Santa Maria Novella, Florence.SCALA/Art Resource, New York
Aristotle’s ethical writings were not known to scholars in western Europe during Abelard’s time. Latin translations became available only in the first half of the 13th century, and the rediscovery of Aristotle dominated later medieval philosophy. Nowhere is his influence more marked than in the thought of St. Thomas Aquinas (1225–74), who is often regarded as the greatest of the Scholastic philosophers and is undoubtedly the most influential, since his teachings became the semiofficial philosophy of the Roman Catholic Church. Such is the respect in which Aquinas held Aristotle that he referred to him simply as The Philosopher. Indeed, it is not too far from the truth to say that the chief aim of Aquinas’s work was to reconcile Aristotle’s views with Christian doctrine.
Aquinas took from Aristotle the notion of an ultimate end, or goal—a summum bonum—at which all human action is directed; and, like Aristotle, he conceived of this end as necessarily connected with happiness. This conception was Christianized, however, by the idea that happiness is to be found in the love of God. Thus, a person seeks to know God but cannot fully succeed in doing so in this life on Earth. The reward of heaven, where one can know God, is available only to those who merit it, though even then it is given by God’s grace rather than obtained by right. Short of heaven, a person can experience only a more limited form of happiness through a life of virtue and friendship, much as Aristotle had recommended.
The blend of Aristotle’s teachings and Christianity is also evident in Aquinas’s views about right and wrong and about how one comes to know the difference between the two. Aquinas is often described as advocating a “natural law” ethic, but this term is easily misunderstood. The natural law to which Aquinas referred does not require a legislator, any more than do the laws of nature that govern the motions of the planets. An even more common mistake is to imagine that this conception of natural law relies on contrasting what is natural with what is artificial. Aquinas’s theory of the basis of right and wrong developed rather as an alternative to the view that morality is determined simply by the arbitrary will of God. Instead of conceiving of right and wrong in this manner as something fundamentally unrelated to human goals and purposes, Aquinas viewed morality as deriving from human nature and the activities that are objectively suited to it.
It is a consequence of this natural law ethics that the difference between right and wrong can be appreciated by the use of reason and reflection on experience. Although Christian revelation may supplement this knowledge in some respects, even pagan philosophers such as Aristotle could understand the essentials of virtuous living. One is, however, likely to err when applying these general principles to the particular cases one confronts in everyday life. Corrupt customs and poor moral education may obscure the conclusions of natural reason. Hence, societies must enact laws of their own to supplement natural law and, where necessary, to coerce those who, because of their own imperfections, are liable to do what is wrong and socially destructive.
It follows too that virtue and human flourishing are linked. When one does what is right, he does what is objectively suited to his true nature. Thus, the promise of heaven is no mere external sanction, rewarding actions to which one would otherwise be indifferent or which may even be against one’s interest. On the contrary, Aquinas wrote that “God is not offended by us except by what we do against our own good.” Reward and punishment in the afterlife reinforce a moral law that all humans, Christian as well as pagan, have adequate prior reasons for following.
In arguing for his views, Aquinas was always concerned to show that he had the authority of the Scriptures or the Church Fathers on his side, but the substance of his ethical system is to a remarkable degree based on reason rather than revelation. This is strong testimony to the power of Aristotle’s example. Nonetheless, Aquinas absorbed the weaknesses as well as the strengths of the Aristotelian system. In particular, his attempt to base right and wrong on human nature invites the objection that one cannot presuppose human nature to be good. Aquinas might reply that it is good because God made it so, but this merely pushes back one step the issue of the basis of good and bad: Did God make human nature good in accordance with some independent standard of goodness, or would any human nature made by God be good? If one gives the former answer, then one needs an account of the independent standard of goodness. Because this standard cannot be based on human nature (for then the argument would be circular), it is not clear what account Aquinas could offer. If one maintains that any human nature made by God would be good, then one must accept that, if God had made human nature such that humans flourish and achieve happiness by torturing the weak and helpless, that would have been what humans should do in order to live virtuously.
Something resembling this second option—but without the intermediate step of an appeal to human nature—was the position taken by the last of the great Scholastic philosophers, William of Ockham (c. 1285–1347/49). Ockham boldly broke with much that had been taken for granted by his immediate predecessors. Fundamental to his approach was his rejection of the central Aristotelian idea that all things have an ultimate end toward which they naturally tend. He therefore also spurned Aquinas’s attempt to base morality on human nature and with it the idea that goodness is closely connected with happiness, which is the ultimate end of human beings. Ockham was thus led to a position that contrasted starkly with almost all previous ethical doctrines in the West. Ockham denied all standards of good and evil that are independent of God’s will. What God wills is good; what God condemns is evil. That is all there is to say about the matter. This position is sometimes called a divine approbation theory, because it defines good as whatever is approved by God. As mentioned earlier, it follows from such a position that it is meaningless to describe God himself as good. It also follows that if God had willed humans to torture children, it would be good to do so. As for the actual content of God’s will, according to Ockham, that is not a subject for philosophy but rather a matter for revelation and faith.
The rigour and consistency of Ockham’s philosophy made it for a time one of the leading schools of Scholastic thought, but eventually it was the philosophy of Aquinas that prevailed in the Roman Catholic Church. After the Reformation, however, Ockham’s view was influential among Protestant theologians. Meanwhile, it hastened the decline of Scholastic moral philosophy, because it effectively removed ethics from the sphere of reason. The Renaissance and the Reformation