The Music of the Heavens: Kepler's Harmonic Astronomy.

The current volume is to some degree a companion piece to Stephenson's Kepler's Physical Astronomy (New York: Springer-Verlag, 1987), doing for book five of Kepler's Harmonice mundi what the earlier work did for his Astronomia nova. Each gives a excellent, readable explication of the relevant text, explaining the astronomy and mathematics and showing how Kepler arrived at his conclusions. But the Harmonice mundi had a more ambitious aim than the Astronomia nova. In the Harmonice mundi Kepler meant to show how mathematics, music, astrology, and astronomy fit harmonically into the divine plan of creation. Book five dealt with astronomy, and in it Kepler revealed his third "harmonic" law. Kepler considered this the crowning work of his career, but even during his lifetime it was rarely read. "Soon after birth," Stephenson tells us, his harmonic ideas "fell into a kind of limbo, from which they have never emerged: too technical to be read by those who listen for the music of the spheres, and too peculiar to be taken seriously by scientists with the technical ability to understand them" (243). Stephenson describes the work of two authors who did try to grapple with Kepler's complicated theories, the English astronomer Jeremiah Horrocks and the Italian Jesuit Giovanni Battista Riccioli (who wrote on the history of astronomy), and he is the first to give these authors deserved recognition.

Stephenson discusses the tradition of universal harmonies. He goes through the harmonic theories of Plato, Ptolemy, and Boethius, and gives special attention to Jofrancus Offusius, who tried to establish a scientific astrology based on universal harmony. But Ptolemy's Harmonics provided special inspiration for Kepler. He even suggested that he wanted to bring out a new edition and Latin translation of Ptolemy's work. Kepler believed that Ptolemy's idea of universal harmonies was viable; only his astronomy and mathematics was outdated. Kepler was convinced that modern astronomical and mathematical ideas (namely his own) and baroque musical theories would furnish the background for a sophisticated, accurate harmonics. The Mysterium cosmographicum, Kepler's earliest astronomical work where he described the distances between the planets as proportional to the five regular polyhedra, provided Kepler's vision of the architecture of the universe. Scholars have noted that this theory may be incorrect, but this first book was fruitful in setting up the main lines of Kepler's thought. In particular they have mentioned the origins of his physical theory of planetary motion in his discussion of motive souls, and yet, Stephenson maintains, the harmonic theories that he first started developing four years later provided a better basis for that theory.

Kepler's writings on universal harmonies have been greeted by many scholars as proof of his mysticism, and this is one point that Stephenson is at pains to dispel. The belief that the universe was created according to a divine plan was common to astronomers in the seventeenth century. Stephenson claims that there is nothing irrational (that is, mystical) in Kepler's theories in the context of the seventeenth century. I agree with Stephenson on this point; however, he does not situate his discussion within the context of seventeenth century mysticism so that his argument falls short. Stephenson's remarks are important, but they would best be supplemented by the discussion of Kepler's astronomy and Renaissance Neoplatonism by J.V. Field in Kepler's Geometrical Cosmology (Chicago: University of Chicago Press, 1988).

SHEILA J. RABIN St. Peter's College