The Copernican Question: Prognostication, Skepticism, and Celestial Order

The Copernican Question: Prognostication, Skepticism, and Celestial Order

The Copernican Question: Prognostication, Skepticism, and Celestial Order

The Copernican Question: Prognostication, Skepticism, and Celestial Order

Synopsis

In 1543, Nicolaus Copernicus publicly defended his hypothesis that the earth is a planet and the sun a body resting near the center of a finite universe. But why did Copernicus make this bold proposal? And why did it matter? The Copernican Question reframes this pivotal moment in the history of science, centering the story on a conflict over the credibility of astrology that erupted in Italy just as Copernicus arrived in 1496. Copernicus engendered enormous resistance when he sought to protect astrology by reconstituting its astronomical foundations. Robert S. Westman shows that efforts to answer the astrological skeptics became a crucial unifying theme of the early modern scientific movement. His interpretation of this "long sixteenth century," from the 1490s to the 1610s, offers a new framework for understanding the great transformations in natural philosophy in the century that followed.

Excerpt

Is the Earth motionless at the center of a finite, star-studded sphere, or is it a planet moving in an annual circuit around the center? Medieval scholastic natural philosophers debated all sorts of imaginative questions of this kind: whether there are, or could be, more worlds; if there were several worlds, whether the earth of one could be moved naturally to the center of another; whether the spots appearing on the Moon arise from differences in parts of the Moon or from something external; whether the Earth is fixed in the middle of the world and has the same center of gravity; and whether the Earth rotates around its axis.

There were two motivations for entertaining such alternative possibilities. the first arose from natural philosophers answering theological worries about threats to God’s unlimited, absolute power: for example, could God not make several worlds, if he so wished? But the second source of alternatives was already built into Aristotle’s argumentational and rhetorical practices. Aristotle frequently reported the claims of his predecessors only to reject them in favor of his own positions. One such view was that of the Pythagoreans, who “affirm[ed] that the center is occupied by fire, and that the earth is one of the stars, and creates night and day as it travels in a circle about the center.” From the thirteenth to the seventeenth centuries, Aristotle’s description of the Pythagorean view became a standard part of the argument that students learned—and then learned to reject—in support of the Earth’s centrality and immobility. It was only sometime in the last years of the fifteenth and the first decade of the sixteenth century that a Polish church canon and sometime astronomical practitioner named Nicolaus Copernicus posed the Pythagorean idea to himself in a new way. He did so not in the thirteenth-century-philosophical style, as an alternative to be rejected, but rather as a mathematical assumption in the style of Claudius Ptolemy, reinterpreting the old Pythagorean idea as an astronomical explanation for two perplexing problems: first, the Sun’s apparent motion as mirrored in the planets’ motions, and second, the disputed ordering of Venus and Mercury. Yet not until 1543 did Copernicus finally publish a full-dress defense of this explanation and mobilize it as a vehicle for persuading others.

The Copernican Question opens with a paradox of historical context. Why ever did Copernicus concern himself about the order of the planets when the burgeoning late-fifteenth and early-sixteenthcentury heavenly print literature, directed to learned elites and ordinary people alike, was overwhelmingly preoccupied with astrologically driven anticipations of the future, sometimes coupled with powerful apocalyptic fantasies that the world would soon come to an end? For those who read Copernicus’s book, De Revolutionibus Orbium Coelestium (On the Revolutions of the Heavenly Spheres), what did getting the structure of the heavens right have to do with more accurately predicting the future? and with printing tech-

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