Much of this transformation had been prepared by Italian scholarly initiative in the early 15th century. Lorenzo Valla (1407–57), an antiauthoritarian humanist, used the recently discovered manuscript of Institutio oratoria by Quintilian (35–c. 96) to create new forms of rhetoric and textual criticism. But even more important was the rebirth of an enthusiasm for the philosophy of Plato in Medici Florence and at the cultivated court of Urbino. Precisely to service this enthusiasm, Marsilio Ficino (1433–99), head of the Platonic Academy, translated the entire Platonic corpus into Latin by the end of the 15th century.
Except in the writings of Pico della Mirandola and of the Italian philosopher Giordano Bruno (1548–1600), the direct influence of Platonism on Renaissance metaphysics is difficult to trace. The Platonic account of the moral virtues, however, was admirably adapted to the requirements of Renaissance education, serving as a philosophical foundation of the Renaissance ideal of the courtier and gentleman. But Plato also represented the importance of mathematics and the Pythagorean attempt to discover the secrets of the heavens, the Earth, and the world of nature in terms of number and exact calculation. This aspect of Platonism influenced Renaissance science as well as philosophy. The scientists Nicolaus Copernicus (1473–1543), Johannes Kepler (1571–1630), and Galileo Galilei (1564–1642) owe a great deal to the general climate of Pythagorean confidence in the explanatory power of number.
Kepler, JohannesJohannes Kepler, oil painting by an unknown artist, 1627; in the cathedral of Strasbourg, France.Erich Lessing/Art Resource, New York
Platonism also affected the literary forms in which Renaissance philosophy was written. Although very early medieval Platonists, such as St. Augustine and John Scotus Erigena, occasionally used the dialogue form, later Scholastics abandoned it in favour of the formal treatise, of which the great “summae” of Alexander of Hales (c. 1170–1245) and Aquinas were pristine examples. The Renaissance rediscovery of the Platonic dialogues suggested the literary charm of this conversational method to humanists, scientists, and political philosophers alike. Bruno put forth his central insights in a dialogue, Concerning the Cause, Principle, and One (1584); Galileo presented his novel mechanics in his Dialogue Concerning the Two Chief World Systems—Ptolemaic and Copernican (1632); and even Machiavelli’s The Art of War (1521) takes the form of a genteel conversation in a quiet Florentine garden.
Renaissance humanism was primarily a moral and a literary, rather than a narrowly philosophical, movement. It flowered in figures with broadly philosophical interests, such as Desiderius Erasmus (1469–1536), the erudite citizen of the world, and Sir Thomas More (1477–1535), the learned but unfortunate chancellor of Henry VIII, as well as, in the next generation, the great French essayist Michel de Montaigne (1532–92). But the recovery of the Greek and Latin classics, which was the work of humanism, profoundly affected the entire field of Renaissance and early modern philosophy and science through the ancient schools of philosophy to which it once more directed attention. In addition to Platonism, the most notable of these schools were atomism,Skepticism" class="md-crosslink"> Skepticism, and Stoicism. The discovery of Lucretius’s De rerum natura influenced Galileo, Bruno, and later Pierre Gassendi (1592–1655), a modern Epicurean, through the insights into nature reflected in this work. The recovery of Sextus Empiricus’s Outlines of Pyrrhonism, reprinted in 1562, produced a skeptical crisis in French philosophy that dominated the period from Montaigne to Descartes. And the Stoicism of Seneca and Epictetus became almost the official ethics of the Renaissance, figuring prominently in the Essays (1580–88) of Montaigne, in the letters that Descartes wrote to Princess Elizabeth of Bohemia (1618–79) and to Queen Christina of Sweden (1626–89), and in the later sections of the Ethics (1675) of Benedict de Spinoza (1632–77). Philosophy of nature
Philosophy in the modern world is a self-conscious discipline. It has managed to define itself narrowly, distinguishing itself on the one hand from religion and on the other from exact science. But this narrowing of focus came about very late in its history—certainly not before the 18th century. The earliest philosophers of ancient Greece were theorists of the physical world; Pythagoras and Plato were at once philosophers and mathematicians, and in Aristotle there is no clear distinction between philosophy and natural science. The Renaissance and early modern period continued this breadth of conception characteristic of the Greeks. Galileo and Descartes were at once mathematicians, physicists, and philosophers; and physics retained the name natural philosophy at least until the death of Sir Isaac Newton (1642–1727).
Had the thinkers of the Renaissance been painstaking in the matter of definition (which they were not), they might have defined philosophy, on the basis of its actual practice, as “the rational, methodical, and systematic consideration of humankind, civil society, and the natural world.” Philosophy’s areas of interest would thus not have been in doubt, though the issue of what constitutes “rational, methodical, and systematic consideration” would have been extremely controversial. Because knowledge advances through the discovery and advocacy of new philosophical methods and because these diverse methods depend for their validity on prevailing philosophical criteria of truth, meaning, and importance, the crucial philosophical quarrels of the 16th and 17th centuries were at bottom quarrels about method. It is this issue, rather than any disagreement over subject matter or areas of interest, that divided the greatest Renaissance philosophers.
The great new fact that confronted the Renaissance was the immediacy, the immensity, and the uniformity of the natural world. But what was of primary importance was the new perspective through which this fact was interpreted. To the Schoolmen of the Middle Ages, the universe was hierarchical, organic, and God-ordained. To the philosophers of the Renaissance, it was pluralistic, machinelike, and mathematically ordered. In the Middle Ages, scholars thought in terms of purposes, goals, and divine intentions; in the Renaissance, they thought in terms of forces, mechanical agencies, and physical causes. All of this had become clear by the end of the 15th century. Within the early pages of the Notebooks of Leonardo da Vinci (1452–1519), the great Florentine artist and polymath, occur the following three propositions:
Self-portrait by Leonardo da Vinci, chalk drawing, 1512; in the Palazzo Reale, Turin, Italy.Alinari/Art Resource, New York
1. Since experience has been the mistress of whoever has written well, I take her as my mistress, and to her on all points make my appeal.
2. Instrumental or mechanical science is the noblest and above all others the most useful, seeing that by means of it all animated bodies which have movement perform all their actions.
3. There is no certainty where one can neither apply any of the mathematical sciences, nor any of those which are based upon the mathematical sciences.