Boner, P. J., 2013, Kepler's Cosmological Synthesis: Astrology, Mechanism and the Soul, 159-60.
Kepler described the aspects and consonances as “different peoples, as it were,” who came from “the same country of Geometry.” Essentially, they originated from the same set of principles in different ways. In the case of the consonances, the section of the circumference of a circle corresponding to the side of an inscribed polygon was extended in a straight line and compared in length with the remaining part of the circumference. Kepler compared this departure from the circle to the foundation of a new colony, where the consonances, “living by their own laws,” had established a certain distance from their circular origins. The aspects, on the other hand, were thought to rely completely on the circle for their determination. While the length of a line measured by the side of an inscribed polygon lay at the heart of every consonance, no such feature could be found in the geometrical formulation of an aspect. An aspect was determined entirely by the inscription of congruent and constructible polygons in a circle. “The aspects, remaining within their own country, the circle,” Kepler wrote, “make use of no other laws than those which the roundness of the circle prescribes to them.” These figures had been found among the regular plane figures, Kepler wrote, and were “congruent and inscribed in a circle.”
Despite their different origins, the aspects and consonances relied similarly on the soul for their recognition. Kepler defined an aspect as “a thing of reason” whose influence could not be conveyed immediately, “as if rain and similar things came down from the heavens themselves,” but objectively by an animate faculty. “If there were no soul in the earth,” Kepler wrote, the sun, moon, and planets would have no astrological influence, “either on their own or through any suitable aspect.” And while the harmonies he identified among the motions of those celestial bodies were not audible, they were thought to resonate with a higher faculty of the soul. In fact, the celestial harmonies involved some of the same relations the soul made instinctually when it enjoyed a musical melody. Kepler claimed that the consonances were not simply created by the fluctuation of the air but consisted more fundamentally in harmonic proportions produced by the human voice as well as the motions of the planets. For the perception of these proportions, Kepler referred to the ability of the soul to identify and appreciate their archetypal essence. In the same way the motions of the planets expressed the archetypal principles of the consonances, Kepler argued, the configuration of the heavens exemplified similar principles that found their resonance in the soul of the earth. “It suffices that there is a soul,” Kepler wrote, “which perceives those proportions when they exist and is stirred up by them.”
Boner, P. J., 2013, Kepler's Cosmological Synthesis: Astrology, Mechanism and the Soul. Leiden/ Boston: Brill.
