1 The Birth of Science - MSRI

314 11. The Age-Long Recovery
Later he relates the masses of the three zones:
Since these three bodies are analogous to the center of the sphere, the
surface and the in-between, the symbols of the three persons of the
Holy Trinity, it is plausible that each one of them has as much matter
as each of the other two[.] 91
Continuing in this vein, he manages to determine the thickness of the
sphere of fixed stars as one twelve-thousandth of the diameter of the sun:
in his reckoning, a bit over 2000 German miles.
The eclecticism of Kepler and his colleagues had the important function
of allowing the recovery of some ancient scientific knowledge that had
been disguised and filtered through nonscientific traditions. Some other
Keplerian passages will help make this point clear:
The perfection of the world consists in light, heat, motion and the
harmony of motions . . . Regarding light, the majestic sun itself is
light, and as it were the eye of the world; and it lights up, colors and
beautifies everything else in the world, like a fountain of light or a
very bright torch[.]
Regarding fire, the sun is the hearth of the world . . . The sun is fire, as
the Pythagoreans said . . . [It is] as if a vegetative faculty were present
not only in earthly creatures but also in all of ether throughout the
whole expanse of the universe, a supposition thrust upon us by the
sun’s obvious heating energy. . . ; it is plausible that this faculty inheres
in the sun as the heart of the world, and that it diffuses from
there, as vehicle of light, together with heat, throughout the enormous
amplitude of the universe, just as, in an animal, the seat of
heat and of vital faculties lies in the heart[.]
Regarding motion, the sun is the prime cause of movement of the
planets and the prime mover of the universe[.] 92
So it is the sun that makes the planets move in circles. . . ? But how
can it do this, if it lacks hands with which to grip them. . . ? Instead
of hands it uses the power of its own body, sent out in straight lines
through the vastness of the word[.] 93
We recognize some of Kepler’s sources: the last quote echoes passages
of Vitruvius and Pliny that we have discussed; the rest we have seen, in
almost the same words, in Theon of Smyrna. 94 The idea of a gravitational
91 J. Kepler, Epitome . . . , book IV, first part, near end of section IV = [Kepler: OO], vol. VI, p. 334.
92 J. Kepler, Epitome . . . , book IV, first part, section I = [Kepler: OO], vol. VI, pp. 310–311.
93 J. Kepler, Epitome . . . , book IV, second part, section III = [Kepler: OO], vol. VI, p. 344.
94 See pages 257–258 for Vitruvius and Pliny, and page 274 for Theon.
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