Moral

Although Aristotelianism dominated ethics in the West well into the seventeenth century, the Renaissance witnessed the recovery of other ancient traditions of moral philosophy. As had happened with Aristotle's ethical thought in the Middle Ages, the acceptability of these revived philosophies was largely conditioned by their compatibility with Christianity. The Florentine priest and philosopher Marsilio Ficino (1433–1499), who played the key role in the fifteenth-century revival of Platonism, stressed the extent to which the doctrines of Plato, unlike those of his student Aristotle, were in accord with Christianity. Ficino demonstrated this agreement most successfully in relation to moral philosophy through his influential theory of Platonic love, in which Plato's intellectual ascent from physical beauty to the realm of Ideas was interpreted as a spiritual journey whose final destination was God.

Stoic ethics inspired admiration from many Renaissance thinkers on account of its high-minded principle that virtue alone was sufficient for the good life. Yet its stern moral demands, which included a complete eradication of the emotions, provoked an equal amount of criticism for requiring a superhuman strength that surpassed even the powers of Christ, who had given way to both anger and sorrow. This ambivalent attitude toward Stoic moral philosophy was not overcome until the late sixteenth century, when a new brand of Stoicism, more accommodated to Christianity, was promoted by the Flemish humanist Justus Lipsius (1547–1606). The Spaniard Francisco de Quevedo (1580–1645) attempted to carry forward Lipsius's program of Christianizing Stoicism by claiming that the ultimate source of the philosophy of patient resignation recommended by the Greek Stoic Epictetus (c. 55–135) was the Book of Job. The recovery of Stoic moral philosophy, with its belief that human beings through their reason can comprehend and participate in the rational order of nature, contributed to renewed interest in natural-law theory.

Compared to Platonism and Stoicism, Epicurean moral philosophy made very few inroads into Renaissance thought. Epicurus's doctrine that pleasure was the supreme good, mis-interpreted since antiquity as an endorsement of sensual indulgence, combined with his rejection of divine providence and immortality, rendered his philosophy unacceptable to Christians. Not surprisingly, serious attempts to adapt Epicureanism to Christianity were rare. When the Italian humanist Lorenzo Valla (1407–1457) transferred the earthly pleasures of Epicurus to the heavenly ones enjoyed by the virtuous in the next life, his aim was less to rehabilitate the ancient philosophy than to reassess Christian theology. Similarly, the Dutch humanist Desiderius Erasmus (1466?–1536), by maintaining that Christ was the true Epicurean, since his disciples led the most pleasurable life, sought to highlight the ethical dimension of Christian piety.

The first Renaissance thinker to tap the ethical potential of Pyrrhonian skepticism, which held that it was impossible to attain certain knowledge, was the French essayist Michel de Montaigne (1533–1592). Adopting the motto Que sais-je? (What do I know?), he deployed skeptical arguments to undermine any claims to moral knowledge, in the hope of deflating human presumption, which he regarded as the root of all evil. The recovery of skepticism was part and parcel of the Renaissance movement to revive ancient philosophical traditions. Yet it presented epistemological challenges that in the following era would turn moral philosophy from a discipline based on classical and Christian authority to one founded on principles that had been rationally deduced from self-evident axioms.