of the planets and discovered the three laws of planetary motion that were to lead to
Newton’s law of universal gravitation. In 1600, Kepler became assistant to Tycho
Brahe, succeeding him as court astronomer to Rudolf II. Kepler was deeply mystical,
and many of his astronomical discoveries were motivated by a desire to demonstrate
that a neoplatonic/Pythagorean mathematical order governed the heavens.
The son of peasants, Kepler erected horoscopes and published almanacs to sup-
plement his income as court astronomer. On the title page of De fundamentis,Kepler
inscribed, “Discover the force of Heavens O Men: once recognized it can be put to
use.” He asserted that astrological influence “is so convincing that it can be denied
only by those who had not examined it.” He also said, “We cannot deny the influence
of the stars, without disbelieving in the wisdom of God.”
In much the same way as Saint Thomas Aquinas, Kepler felt that human
beings could rise above planetary influences. As do contemporary astrologers, he thus
cast his predictions in terms of tendencies and probabilities rather than in terms of
absolute fate. Kepler’s contribution to astrology was his general theory of aspects, and
he also invented the quintile, the biquintile, and the sesquiquadrate. Kepler died
November 15, 1630.
Kepler is well known to modern science as the discoverer of the three laws of
planetary motion named after him. His achievements were momentous, coming on
the heels of the Copernican revolution and creating an astronomy of the solar system
that was vastly superior to that existing before.
As an astrologer, Kepler’s achievements were equally, if not more, substantial.
Like his contemporary, Shakespeare, he was “myriad minded.” His thinking ranged
from the most traditionally Judeo-Christian and Pythagorean in his mysticism, to the
most astonishingly modern in his more scientific thinking modes. Full of apparent
contradictions, he was in reality the most complex of thinkers in astronomy and
astrology, and yet, in some ways, was fundamentally quite consistent. Furthermore, he
was a superb writer—lucid and simple, and capable of describing great intricacies
clearly, as well as clothing some of his thoughts in magnificent poetic metaphors.
The supposed separation of astronomy and astrology is actually an illusion as
far as Kepler was concerned. The contemporary scientific community in particular
has all too often been the victim of this illusion, and has oversimplified Kepler’s
alleged “attacks” on astrology, which are actually heated objections to “bad” astrolo-
gy and nothing more. The following in particular is a case in point, from his Tertius
Interveniens:
This curiosity [about astrology] flourishes, and stimulates one to learn
astronomy. And astronomy is not rejected, but highly praised, as is
appropriate. Now this Astrology is a foolish daughter.... But dear Lord,
what would happen to her mother, the highly reasonable Astronomy, if
she did not have this foolish daughter. The world, after all, is much
more foolish, indeed is so foolish, that this old sensible mother, Astron-
omy, is talked into things and put to the lie as a result of her daughter’s
foolish pranks.... The mathematician’s pay would be so low, that the
mother would starve, if the daughter did not earn anything.Kepler, Johannes
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