‘The soul of the newly born baby is marked for life by the pattern of the stars at the moment it comes into the world, unconsciously remembers it, and remains sensitive to the return of configurations of a similar kind.’
Kepler was convinced that the geometrical things have provided the Creator with the model for decorating the whole world”. In Harmonic Mundi , he attempted to explain the proportions of the natural world—particularly the astronomical and astrological aspects .Soon after publishing Harmonices Mundi, Kepler was embroiled in a priority dispute with Robert Fludd, who had recently published his own harmonic theory.
Kepler began by exploring regular polygons and regular solids, including the figures that would come to be known as Kepler’s solids. From there, he extended his harmonic analysis to music, meteorology, and astrology; harmony resulted from the tones made by the souls of heavenly bodies and in the case of astrology, the interaction between those tones and human souls. In the final portion of the work, Kepler dealt with planetary motions, especially relationships between orbital velocity and orbital distance from the Sun. Similar relationships had been used by other astronomers, but Kepler with Tycho’s data and his own astronomical theories treated them much more precisely and attached new physical significance to them.
Yet, it would be a mistake to take Kepler’s astrological interests as merely pecuniary. As one historian, John North, put it, “had he not been an astrologer he would very probably have failed to produce his planetary astronomy in the form we have it.” However, Kepler’s views on astrology were quite unconventional for his time; he argued for a system of astrology based largely on harmonics, a type of ‘planetary harmonics’ based almost entirely upon the astrological aspects and what has been traditionally been termed “the music of the spheres.” Information relating to his theories can be found in his book Harmonice Mundi.
Kepler believed in astrology in the sense that he was convinced that astrological aspects physically and really affected humans as well as the weather on Earth.
He strove to unravel how and why that was the case and tried to put astrology on a surer footing, which resulted in the On the More Certain Fundamentals of Astrology (1601), in which, among other technical innovations, he was the first to propose a number of new aspects such as 18°, 24°, 30° (semisextile),36°, 45° (semi-square), 72° (quintile), 108°, 135° (sesquiquadrate), 144° (bi-quintile),and 150° (quincunx).
In The Intervening Third Man, or a warning to theologians, physicians and philosophers (1610), posing as a third man between the two extreme positions for and against astrology, Kepler advocated that a definite relationship between heavenly phenomena and earthly events could be established.
At least 800 horoscopes and natal charts drawn up by Kepler are still extant, several of himself and his family, accompanied by some unflattering remarks. As part of his duties as district mathematician to Graz, Kepler issued a prognostication for 1595 in which he forecasts peasant uprising, Turkish invasion and bitter cold, all of which happened and brought him renown.
Kepler is known to have compiled prognostications for 1595 to 1606, and from 1617 to 1624. As court mathematician, Kepler explained to Rudolf II the horoscopes of the Emperor Augustus and the Prophet Muhammad, and Kepler gave astrological prognosis for the outcome of a war between the Republic of Venice and Paul V. In the On the new star (1606) Kepler explicated the meaning of the new star of 1604 as the conversion of America, downfall of Islam and return of Christ. The De cometis libelli tres (1619) is also replete with astrological predictions.