Editing Johannes Kepler (section)

== Astrology ==
[[File:Kepler-Wallenstein-Horoskop.jpg|thumb|upright=0.9|Kepler's horoscope for [[General Wallenstein]]]]
Like [[Ptolemy]], Kepler considered astrology as the counterpart to astronomy, and as being of equal interest and value. However, in the following years, the two subjects drifted apart until astrology was no longer practiced among professional astronomers.<ref name=":0">{{Cite journal|last=Field|first=J. V.|date=1984|title=A Lutheran Astrologer: Johannes Kepler|url=https://www.jstor.org/stable/41133735|journal=Archive for History of Exact Sciences|volume=31|issue=3|pages=189–272|doi=10.1007/BF00327703|jstor=41133735|bibcode=1984AHES...31..189F|s2cid=119811074|issn=0003-9519}}</ref>

[[Sir Oliver Lodge]] observed that Kepler was somewhat disdainful of astrology in his own day, as he was "continually attacking and throwing sarcasm at astrology, but it was the only thing for which people would pay him, and on it after a fashion he lived.<ref>{{cite book|author-link=Oliver Lodge |author=Lodge, O. J. |contribution=Johann Kepler |title=The World of Mathematics, Vol. 1 |year=1956 |editor-link=James R. Newman |editor=Newman, J. R. |publisher=[[Simon and Schuster]] |page=231}}</ref> Nonetheless, Kepler spent a huge amount of time trying to restore astrology on a firmer philosophical footing, composing numerous astrological calendars, more than 800 nativities, and a number of treaties dealing with the subject of astrology proper.<ref>{{Cite journal|last=Boner|first=P. J.|date=2005|title=Soul-Searching with Kepler: An Analysis of Anima in His Astrology|url=https://doi.org/10.1177/002182860503600102|journal=Journal for the History of Astronomy|language=en|volume=36|issue=1|pages=7–20|doi=10.1177/002182860503600102|bibcode=2005JHA....36....7B|s2cid=124764022}}</ref>

=== ''De Fundamentis'' ===
In his bid to become imperial astronomer, Kepler wrote ''De Fundamentis'' (1601), whose full title can be translated as "On Giving Astrology Sounder Foundations", as a short foreword to one of his yearly almanacs.<ref>{{Cite journal|last=Simon|first=G.|date=1975|title=Kepler's astrology: The direction of a reform|url=https://www.sciencedirect.com/science/article/abs/pii/0083665675901221|journal=Vistas in Astronomy|language=en|volume=18|issue=1|pages=439–448|doi=10.1016/0083-6656(75)90122-1|bibcode=1975VA.....18..439S}}</ref>

In this work, Kepler describes the effects of the Sun, Moon, and the planets in terms of their light and their influences upon humors, concluding with Kepler's view that the Earth possesses a soul with some sense of geometry. Stimulated by the geometric convergence of rays formed around it, the [[Anima mundi|world-soul]] is sentient but not conscious. As a shepherd is pleased by the piping of a flute without understanding the theory of musical harmony, so likewise Earth responds to the angles and aspects made by the heavens but not in a conscious manner. Eclipses are important as omens because the animal faculty of the Earth is violently disturbed by the sudden intermission of light, experiencing something like emotion and persisting in it for some time.<ref name=":0" />

Kepler surmises that the Earth has "cycles of humors" as living animals do, and provides as an example: "the highest tides of the sea are said by sailors to return after nineteen years around the same days of the year". (This may refer to the 18.6-year [[Lunar node#Effect on tides|lunar node precession cycle]].) Kepler advocates searching for such cycles by gathering observations over a period of many years, "and so far this observation has not been made".<ref>{{Cite journal |last1=Brackenridge |first1=J. Bruce |last2=Rossi |first2=Mary Ann |date=1979 |title=Johannes Kepler's on the More Certain Fundamentals of Astrology Prague 1601 |url=https://www.jstor.org/stable/986232 |journal=Proceedings of the American Philosophical Society |volume=123 |issue=2 |pages=85–116 |jstor=986232 |issn=0003-049X}}</ref>

=== ''Tertius Interveniens'' ===
Kepler and [[Helisaeus Roeslin]] engaged in a series of published attacks and counter-attacks on the importance of astrology after the supernova of 1604; around the same time, physician Philip Feselius published a work dismissing astrology altogether (and Roeslin's work in particular).<ref>Caspar, ''Kepler'', pp.&nbsp;178–181</ref>

In response to what Kepler saw as the excesses of astrology, on the one hand, and overzealous rejection of it, on the other, Kepler prepared ''Tertius Interveniens'' (1610). Nominally this work—presented to the common patron of Roeslin and Feselius—was a neutral mediation between the feuding scholars (the titled meaning "Third-party interventions"), but it also set out Kepler's general views on the value of astrology, including some hypothesized mechanisms of interaction between planets and individual souls. While Kepler considered most traditional rules and methods of astrology to be the "evil-smelling dung" in which "an industrious hen" scrapes, there was an "occasional grain-seed, indeed, even a pearl or a gold nugget" to be found by the conscientious scientific astrologer.<ref>Caspar, ''Kepler'', pp.&nbsp;181–185. The full title is ''Tertius Interveniens, das ist Warnung an etliche Theologos, Medicos vnd Philosophos, sonderlich D. Philippum Feselium, dass sie bey billicher Verwerffung der Sternguckerischen Aberglauben nict das Kindt mit dem Badt aussschütten vnd hiermit jhrer Profession vnwissendt zuwider handlen'', translated by [[C. Doris Hellman]] as "''Tertius Interveniens'', that is warning to some theologians, medics and philosophers, especially D. Philip Feselius, that they in cheap condemnation of the star-gazer's superstition do not throw out the child with the bath and hereby unknowingly act contrary to their profession."</ref>