Three

The city-states’ vigorous competition with one another often escalated into war and rebellion. Their hardball politics was exemplified in the works of Niccolò Machiavelli, a career diplomat who negotiated the surrender of Pisa to Florence but wound up being tortured on the rack by the Medici. In his book The Prince, which he wrote upon retiring to the country after having lost one political battle too many, Machiavelli advises that “it is far safer to be feared than loved,” adding that “being unarmed…causes you to be despised” and that “a prince ought to have no other aim or thought…than war.” Small wonder that Baldassare Castiglione, in his internationally popular A Manual for Gentlemen of 1528—a book praised for its “civilizing” influence—observed that “the principal and true profession of a courtier ought to be in feats of arms.”

But Castiglione added that “the principal matter…is for a courtier to speak and write well.” To minimize crippling losses of blood and treasure, the Italian city-states did two things. First, they trained some of the world’s first professional ambassadors, nurturing staffs of political advisors to guide their leaders and advertise their civic virtues—especially “civic humanism,” the idea, prominent in liberal democracies today, that citizens should devote time to government service. Second, they promoted their ongoing competition in technology and the arts as a peaceful and profitable alternative to war.

Many of the great Renaissance artists were men of common origins who resented being condescended to by aristocrats and by the scholars who aped aristocratic manners. Complained Leonardo, the illegitimate son of a liaison between a lawyer and a young lady said to have been a household servant:

Michelangelo—a brusque, muscular workman who went for months without bathing or taking off his dogskin boots, and whose conspicuously broken nose resulted from a fistfight—was similarly quick to take offense. When Leonardo made fun of him, joking with friends who were disputing some lines of Dante in front of the Palazzo di Gavina that “Michelangelo will explain it to you,” Michelangelo’s response was to question not Leonardo’s art but his technological ability: “You designed a horse to be cast in bronze and, as you could not cast it, you abandoned it from shame—and those stupid Milanese believed in you.” The peerless goldsmith Benvenuto Cellini was a hooligan who boasted in his autobiography of killing four men and of reducing wealthy noblemen to near-groveling as they vied to get him to accept their commissions. Although Cellini’s tales smack of exaggeration, they capture the frustration felt by many artists and artisans whose dexterity brought them money and recognition but inadequate social status.

The making and accounting of money helped advance quantitative modes of analysis without which science might otherwise have stalled at a merely descriptive level. Florentine bankers, Milanese merchants, and Venetian traders created important innovations such as double-entry bookkeeping—which their successors learned from Luca Pacioli’s authoritative Summa de Arithmetica, first published in Venice in 1494—while technological improvements pioneered by the Genoese, Florentine, and Venetian mints gained their coins an international reputation for reliable weight and purity. The minting of money became a subject of scientific interest, with Nicolaus Copernicus publishing a treatise on coinage in Poland in 1526 and Isaac Newton taking control of the London mint from 1699.

Once the printing press had radically reduced the cost of books, scientific and technological innovators found that there was money to be made by writing for the public, in the vernacular rather than Greek or Latin. Their popular books made an end run around the authorities, setting the stage for a dramatic confrontation between tradition and the emerging forces of innovation and creativity. It came in Italy. Its martyr was Galileo.

A born scientist, lifelong experimenter, and compelling writer, Galileo Galilei presented a triple threat to the professors and priests whose careers were invested in the proposition that everything worth knowing could be found in ancient books. (Galileo said that they studied “a world on paper,” whereas his experiments revealed “the real world.”) His iconoclasm appears to have been inherited from his father, the merchant, musician, and mathematician Vincenzio Galilei, who wrote papers disputing scholarly opinions about music that conflicted with experience. When his former teacher Gioseffo Zarlino asserted that the semitone cannot be divided into two equal parts—because to do so meant invoking an irrational number, which is to say a number that cannot be expressed as the ratio of two integers, a Christian taboo—Vincenzio countered that since any capable musician could hear such tones, a mathematical theory that denied their existence must be flawed. To test the prevailing claim that two strings of equal lengths which sound an octave apart must differ in tension by the ratio 2:1, Vincenzio suspended various weights from lyre strings and found that the ratio actually is 4:1. So the young Galileo had plenty of opportunity to see how experimentation could overturn the opinions of scholars.

This seemingly minor observation had epochal implications. The Aristotelian professors taught that heavy objects fall faster than light objects, as everyday experience indicates. Owing to air resistance, coins dropped here on earth fall faster than feathers do. Galileo’s experiments minimized the effect of air resistance, allowing him to glimpse the truth—that gravity accelerates all objects at the same rate, regardless of their mass. With that, Galileo the college dropout opened a door for future scientists from Newton to Einstein and beyond.

In May 1609, having learned that telescopes were being fashioned in the Netherlands, Galileo began making telescopes of his own, turned them on the sky, and embarked on observations that demolished the Aristotelian universe. That model, fashioned in the fourth century BC by Aristotle and the Greek astronomer Eudoxus and refined by Claudius Ptolemy of Alexandria in the second century AD, placed the earth at the center of the universe and depicted the sun, moon, planets, and stars as waferlike discs attached to revolving crystalline spheres. The terrestrial realm had four elements—earth and water, whose gravity made them go downward, and air and fire, whose levity inclined them to rise. Everything above was made of a fifth element, ether, which obeyed a physics all its own. The first four elements could change, but ether could not: Hence the earth was dynamic and the heavens immutable. Flaws in this official cosmology had been observed in the behavior of comets, whose elliptical orbits required that they fly right through the crystalline spheres, and novae—“new” stars, which are actually old stars that explode and become bright enough to be seen for the first time with the unaided eye. When a nova appeared in 1604, Galileo gave three public lectures about it, pointing out that any new apparition in the heavens violated the Aristotelian proscription against change among the heavenly spheres. Such occasional anomalies could be explained away by learned Aristotelians in the Vatican and at the colleges, but Galileo’s telescopic observations ended the argument—or should have. The moon displayed rugged mountains, like the earth’s, only craggier, and in no way resembled an ethereal wafer. Venus displayed phases like the moon’s, indicating that it pursues an orbit around the sun, inside Earth’s orbit, just as depicted in the Copernican cosmology.

Galileo’s book presenting these observations, Sidereus Nuncius (“Messages from the Stars”), created a sensation. With the Italian city-states competing for geniuses in something like the way that its cities today vie for football stars, a newly famous Galileo could take his pick of academic appointments. But he assumed, as scientists sometimes do, that politics was simpler than science, and so made a series of political miscalculations.