Kepler's Astrology
based on an article by David Plant,

To Kepler, the planetary laws represented far more than the description of a physical mechanism. Kepler did not view science and spirituality as mutually exclusive.  His comparison of astrology to the 'foolish daughter' of the 'wise mother' (astronomy) has often been cited as evidence of his disbelief in astrology. Seen in context, however, the foolish daughter represents a particular style of astrology — popular astrology. He was always careful to distinguish his reverential vision of the celestial harmonies from the practices of the backstreet astrologers and almanac-makers "who prefer to engage in mad ravings with the uneducated masses"(1). His disapproval stems from his conviction that astrology (done properly, as he did it) is nothing less than a divine revelation, "...a testimony of God's works and... by no means a frivolous thing".

Unfortunately, Kepler's salary as Imperial Mathematicus was rarely paid (the Imperial treasury owed him 20,000 florins by the end of his career) so he was obliged to scratch out a living by giving astrological advice to wealthy clients and composing astrological almanacs for the 'uneducated masses' he so despised. Reluctantly, Kepler conceded that "the mother would starve if the daughter did not earn anything". His reputation as having a deep understanding of the celestial motions made his astrology highly believable and sought after.

So Kepler was undoubtedly an astrologer — but he was no respecter of astrological tradition. Kepler's astrology was on another plane altogether. His ideas seem radical even by the standards of mainstream astrology today. For a start, he dismissed the use of the 12 houses as 'Arabic sorcery'. While accepting that the angles were important, he could see no justification for conventional house division. "Demonstrate the old houses to me," he wrote to one of his correspondents, "Explain their number; prove that there can be neither fewer nor more... show me undoubted and striking examples of their influence." (2) He even went so far as to question the validity of the signs of the zodiac, arguing that they were derived from human reasoning and arithmetical convenience rather than any natural division of the heavens (3). He had no time for elaborate schemes of planetary sign rulership and saw no reason why some planets should be classed as benefic and others as malefic.

Kepler left no astrological convention unchallenged. His rigorous questioning hints at a massive reformation of astrology, on a scale that has been compared to the reformation that Martin Luther brought about in the Church. More prosaically, it should be seen in the context of the monumental changes taking place in theoretical astronomy during the 16th and 17th centuries. The ancient Aristotelian doctrines that had given astrology some measure of scientific credibility were crumbling fast. Copernicus had displaced the Earth from the center of the universe; Tycho had proved that the 'immutable' heavens were subject to change as new stars blazed in the sky; Galileo's telescope had opened up dimensions undreamt of by Ptolemy; Kepler himself had shattered the serene, circular motions of the planetary orbits forever. He sensed that astrology would have to adjust to the new astronomy if it were to keep pace with the march of science.

The New Aspects

The key to Kepler's proposed reform is his approach to the aspects. Traditional astrology recognizes five significant relationships, based upon the twelvefold division of the zodiac signs. Ptolemy taught that their significance was derived by analogy with the ratios of the musical scale (4). The conjunction is equivalent to the same two notes played in unison. The opposition divides the circle in the ratio 1:2, which corresponds to the octave. The sextile (5:6) corresponds to a minor third, the square (3:4) to a perfect fourth and the trine (2:3) to a perfect fifth. By placing less emphasis upon the zodiac signs, however, Kepler was free to explore additional aspect relationships in his pursuit of the Pythagorean synthesis of music, geometry and astronomy.

Kepler's new aspects were based upon harmonic theory and grounded in empirical observation of astrological effects. From his long-term study of weather conditions correlated with planetary angles and from detailed analysis of his collection of 800 birth charts, Kepler concluded that when planets formed angles equivalent to particular harmonic ratios a resonance was set up, both in the archetypal 'Earth-soul' and in the souls of individuals born under those configurations. He considered this 'celestial imprint' more important than the traditional emphasis on signs and houses: "in the vital power of the human being that is ignited at birth there glows that remembered image..." The geometric-harmonic imprint constitutes "the music that impels the listener to dance" as the movements of the planets, by transit and direction, echo and re-echo the natal theme.

At least 800 horoscopes drawn up by Kepler are still extant. As part of his duties as district mathematician to Graz, Kepler issued a prognostication for 1595 in which he forecast a peasant uprising, Turkish invasion and bitter cold, all of which happened and brought him renown.

One of his horoscopes is shown to the right. It was discovered by Lick Observatory astronomer Anthone Misch in a collection of old manuscripts in the library archives. It documents the birth of an Austrian nobleman named Hans Hannibal Hütter von Hütterhofen, in 1586. That information is inscribed in an ancient flowery hand at the top of the manuscript. What lies below is the work of Kepler, a complicated weaving of signs and zodiacal symbols. (from keplerhoroscope.jpg (138184 bytes)


1 ] Quoted in Kepler's Astrology: Excerpts, selected, translated and edited by Ken Negus (Eucopia Publications 1987). Unless otherwise stated, all quotes by Kepler himself are from this compilation.
2 ] From a letter to the astronomer David Fabricius quoted in Neo-Astrology: a Copernican Revolution by Michel Gauquelin (Arkana 1991), p.92
3 ] Kepler later qualified his criticism of the zodiac signs by remarking that, "...the human race has envisioned this partition from the time of the Chaldeans down to our own time". This being so, he wondered whether "God himself does not conform to it... and whether He does not wish to speak to human beings therewith in a language or method of communication that they understand".
4 ] Ptolemy: Tetrabiblos (Loeb) p.73-5. In Ptolemy's unfinished Harmonics, he proposed the earliest known 'tone-zodiac', linking the 12 signs to musical intervals. This idea has been explored by other astro-musical theorists, notably Rudolph Steiner.