Soul-Searching with Kepler: An Analysis of Anima in His Astrology

References to von Dyck Walther Caspar Max (eds), Johannes Kepler Gesammelte Werke (22 vols, Munich, 1937–), are abbreviated as KGW, with line numbers separated from page numbers by a stop.

In December 1599 Kepler outlined to his patron Herwart von Hohenburg plans for a future publication that eventually took the form of the all-inclusive Harmonice mundi (1619). In this letter, Kepler specified five chapters, corresponding to geometry, arithmetic, music, astrology and astronomy. Traditionally classified with astronomy in an altogether different form, astrology was set aside here as the study of “the causes of the Aspects”. See KGW , xiv, no. 148, 100; and Field Judith V. , Kepler's geometrical cosmology (London, 1988), 96–99, and “A Lutheran astrologer: Johannes Kepler”, Archive for history of exact sciences, xxxi (1984), 189–271, p. 208. On the theological significance of astrology as a part of the Lutheran attitude towards the natural world and the potential impact the educational reforms of Philip Melanchthon had on Kepler, see Barker Peter and Goldstein Bernard R. , “Theological foundations of Kepler's astronomy”, Osiris, xvi (2001), 88–113, and Kusukawa Sachiko , The transformation of natural philosophy: The case of Philip Melanchthon (Cambridge, 1995), 170–1, 188.

On Kepler's comparison of astrology with medicine and how he believed the two relied similarly on empirical evidence, see KGW, iv, 164.9–15 and 177.18–25, and Rabin Sheila J. , “Two Renaissance views of astrology: Pico and Kepler”, Ph.D. dissertation, City University of New York, 1987, 157.

Article-length essays include Hammer Franz , “Die Astrologie des Johannes Kepler”, Sudhoffs Archiv, lv (1971), 113–35; List Martha , “Das Wallenstein-Horoskop von Johannes Kepler”, in Johannes Kepler: Werk und Leistung (Linz, 1971), 127–35; Brackenridge Bruce J. , “Kepler, elliptical orbits, and celestial circularity: A study in the persistence of metaphysical commitment”, Parts I and II, Annals of science , xxxix (1982), 117–43, 265–95; Field , “A Lutheran astrologer” (ref. 1); Rosen Edward , “Kepler's attitude toward astrology and mysticism”, in Occult and scientific mentalities in the Renaissance, ed. by Vickers Brian (Cambridge, 1984), 253–71; Rabin Sheila , “Kepler's attitude toward Pico and the anti-astrology polemic”, Renaissance quarterly, 1 (1997), 750–70; and Westman Robert S. , “Kepler's early physico-astrological problematic”, Journal for the history of astronomy, xxxii (2001), 227–36. By far the most comprehensive book-length account of Kepler's astrology in recent times has been Simon Gérard , Kepler astronome astrologue (Paris, 1979).

For one of Kepler's earliest such discussions, in which he considered in great detail astrology, astronomy, optics and theology in a letter to Herwart von Hohenburg, see Kepler Johannes , KGW, xiii, no. 117, 309.15–315.30.

KGW , vi, 221.8–15: “In Timaeo , qui est citra omnem dubitationis aleam, commentarius quidam in primum caput Geneseos seu lib. I. Mosis, transformans illum in Philosophiam Pythagoricam: Ut facile patet attentè legenti, et verba ipsa Mosis identidem conferenti.” See Martens Rhonda , “A commentary on Genesis: Plato's Timaeus and Kepler's astronomy”, in Plato's Timaeus as cultural icon, ed. by Reydams-Schils Gretchen J. (Notre Dame, 2003), 251–66.

The problem Plato encountered for the first time in the Meno was that of whether knowledge was possible. It is clear from the contents of the Meno that Plato saw in mathematics one of the few fields in which any systematic and organized knowledge had been achieved, and this was a decisive factor in Plato's adoption of his theory of knowledge.

For concise endorsements of this appraisal, see Burtt Edwin A. , The metaphysical foundations of modern physical science (rev. edn, London, 1932), 57–58, 60; Pauli Wolfgang , “The influence of scientific ideas on the scientific theories of Kepler”, in The interpretation of nature and the psyche , ed. by Jung C. G. and Pauli W. (London, 1952), 147–240, p. 152; and Dijksterhuis Eduard J. , The mechanization of the world picture, transl. by Dikshoorn C. (Oxford, 1961), 304.

The ascent from the world of Becoming to the world of Being, from illusion to pure philosophy, was brilliantly illustrated by Plato's well-known cave metaphor in the Republic , 514a–521b.

Plato , Timaeus , transl. by Lee Desmond (London, 1971), 70. Scholars generally agree that Plato's theory of Forms was first introduced in the Phaedo. Here Plato assumed that Forms were universal in the sense that they were applicable to all their sensible instances. As Norman Gulley has noted, Plato's argument presupposed that in bringing to light the Forms the sensibles remained at least relatively constant and that the senses themselves offered only eradicable interference; see Gulley Norman , Plato's theory of knowledge (London, 1962), 36, and Cornford Francis M. , Plato's theory of knowledge: The Theaetetus and the Sophist of Plato (London, 1935), 6.

Desmond Lee, Introduction, Timaeus and Critias (ref. 9), 13. In the Phaedrus, 245c-e, Plato suggested that the essence of the soul was self-motion, and in the Laws, 893b, he defined the soul as that which was capable of moving itself. This conception of soul as a source of movement served as the basis for a demonstration that the order of the world was attributable to the control of a supreme soul; see Gulley , Plato's theory of knowledge (ref. 9), 131.

Plato , Timaeus, transl. by Lee Desmond (ref. 9), 49.

Plato , Phaedrus , transl. by Hamilton Walter (London, 1973), 246–57. Plato's three-part division of the soul was in several ways analogous to his conception of the ideal society in the Republic. In this conception, Plato distinguished three population components: The rigorously recruited ruler class exercised supreme authority, the auxiliary class discharged military, police and executive duties under the orders of the rulers, and the industrial and agricultural class performed much of the practical labour underlying the general well-being of the society. Although in many ways autonomous, all three classes of society were intricately interdependent, much like the divisions of the human soul, and both society and the individual shared a top-down course of cohesiveness and order; the supreme ruling class set a precedent for order that filtered down through the remaining ranks of society, much like the powers of reason generated harmony and stability for the remaining parts of the individual.

Plato , Timaeus, transl. by Lee (ref. 9), 96.

Ibid.

Ibid.

See Plato , Meno , 81c-d. In support of this theory, Socrates elicited geometrical knowledge from a slave-boy in the Meno. The aim of Socrates was to lead the slave-boy, prompted by questions, to the correct solution of the length of the side of a square that had twice the area of a square with sides two feet long. In his more categorical analysis of recollection in the Phaedo, Plato claimed that knowledge of concepts such as equality, which were always imperfectly instantiated in the world, could come only from anamnesis; see Plato , Phaedo, 73a–75d.

For a mythological account of this theory, in which Socrates related the story of a warrior who lived to tell his after-life experience, see Plato , Republic, 614b.

Democritus stated that the soul and the mind were of the same essence, composed of primary and indivisible bodies; he suggested that the mind brought about motion through the sheer size of these bodies and their shape. For Anaxagoras, it was the simple, pure essence of the mind as first principle that made possible the production of motion and cognition. Along these same lines, Diogenes of Apollonia claimed that the soul consisted of air: It was the most finely grained of things and therefore the first principle. Because it was the most basic of things from which everything else derived, Diogenes contended, the soul generated motion on account of its primacy and purity.

Smith Mark A. , “Getting the big picture in perspectivist optics”, Isis, Ixxii (1981), 568–89, p. 576.

In De anima, 412a–b, Aristotle compared the living body and the soul respectively to a wax stamp and its imprint: Both sets could be analysed into Form and matter, but in the exceptional case of living beings their Form could be identified with the concept of soul.

Lawson-Tancred Hugh , Introduction, De anima, transl. by Lawson-Tancred Hugh (London, 1986), 71–73.

Much has been made of Aristotle's active intellect as a potential means of immortality. For an insightful study of the interpretations that emerged from late Antiquity, see Blumenthal H. J. , Aristotle and Neoplatonism in late Antiquity: Interpretations of the De anima (Ithaca, 1996).

Smith's Mark A. analysis of visual perception in the theories of Aristotle and Ptolemy has brought clarity to the cloudy matters of cognition, perception and sensory experience; see Smith Mark A. , “The psychology of visual perception in Ptolemy's optics”, Isis, lxxix (1988), 188–207. Kepler later used the metaphor of the signature ring in a letter to Hohenberg to help explain how momentary configurations of the heavens left lasting impressions on earthly entities; see Kepler Johannes , KGW, xiii, no. 117, 314.7–21.

Shortly after the opening of a letter written to Michael Mästlin in December 1598 ( KGW , xiii, no. 106, 251.5–34), Kepler introduced his investigations on eclipses with an apology: He did not intend for his mentor to see his recently published almanac without first pointing out its faults. Kepler attributed many of its deficiencies to the expectations the intended audience of his almanac would have. Thus, he wrote “neither for the general public nor for the learned”, but rather “for nobles and prelates, who claim for themselves some knowledge of things they do not know”. Despite his claim that he endeavoured in all his prognostica “so as to offer from convictions set out … some certain taste of the pleasantness and greatness of nature”, Kepler apparently was relieved that the number of almanacs would be small enough to ensure that few would ever reach the borders of Germany, where his professional reputation mattered most to those sponsoring his position. As Eloy Rada García has pointed out in his rendering of this letter, Kepler also had good financial reasons for occasionally catering to the tastes of his affluent readership; see García E. R. , n. 17 in Kepler Johannes , El secreto del universo , transl. by García E. R. (Madrid, 1992), 223. For another perspective on Kepler's customization of his astrological writings, see Rutkin Darrel H. , “Celestial offerings: Astrological motifs in the dedicatory letters of Kepler's Astronomia nova and Galileo's Sidereus nuncius”, in Secrets of nature: Astrology and alchemy in early modern Europe, ed. by Newman William R. and Grafton Anthony (Cambridge, MA, 2001), 133–72, esp. pp. 149–50, 155.

In addition to the different ways in which Kepler expressed his views on astrology, he set himself apart in various respects from his fellow practitioners, with particular attention given to the utter rejection of astrology by Giovanni Pico della Mirandola. As Robert S. Westman has noted, “scholars such as Bowen Ellen Mary Field Judith Rabin Sheila , and Grafton Anthony have by now established that Kepler was deeply engaged in what might be considered a running debate with Pico. The position that Kepler sustained fairly consistently throughout these writings was that there was some truth and some falsehood in astrology and the same was true for Pico's critique of it”; see his “Kepler's early physico-astrological problematic” (ref. 3), 230. On Kepler's learned exchanges with Hohenburg, see Grafton Anthony , Defenders of the text: The traditions of scholarship in an age of science, 1450–1800 (Cambridge, MA, 1991), 187–9, and Commerce with the classics: Ancient books and Renaissance readers (Ann Arbor, 1997), 198. On Kepler's crafty use of the comedic in his astrological writings, see Gerlach Walther , “Humor und Witz in Schriften von Johannes Kepler”, Bayerische Akademie der Wissenschaften mathematischnaturwissenschaftliche Klasse Sitzungberichte (Munich, 1968), 23–30.

In considering these collectively, Kepler could also have drawn from the threefold conception of music by Boethius, who divided it into mundana, humana and instrumentalis; see Stephenson Bruce , The music of the heavens: Kepler's harmonic astronomy (Princeton, 1994), 41–44.

Kepler Johannes , The harmony of the world , transl. by Aiton E. J. Duncan A. M. and Field J. V. (Philadelphia, 1997), 294–5; cf. KGW, vi, 215.30–33.

Kepler saw no reason why the Sun should need a sophisticated intellect for its motive functions. The revolution of its body remained constant so as to maintain the same ratio between its motive force and the resistance of the surrounding celestial bodies (this ratio had to remain the same because Kepler, in his adherence to Aristotelian physics, assumed that all motion was produced by constant causation).

See Aiton Eric J. , The vortex theory of planetary motions (NewYork, 1972), 12–19. As Contended Lohne Johannes , Kepler's solar virtus was something entirely different from Newtonian ‘force’ and therefore should not be rendered by the modern mechanical term; see his “Hooke versus Newton: An analysis of the documents in the case on free fall and planetary motion”, Centaurus, vii (1960), 6–52, pp. 7–9. By contrast, Eduard J. Dijksterhuis pointed out the similarities shared by the two seemingly different accounts offered by animate and inanimate explanations of motion. “The only thing that is established with certainty in both cases”, Dijksterhuis has suggested, “is the behaviour. One does not gain a deeper understanding if one gives a name to the unknown cause of this behaviour”; see his The mechanization of the world picture (ref. 7), 310, 312.

On the attenuation of the motive source of the Sun and Kepler's comparison of it to the exemplum of light, see Kepler Johannes , New astronomy , transl. by Donahue William H. (Cambridge, 1992), 383, 394; cf. Barker and Goldstein , “Theological foundations of Kepler's astronomy” (ref. 1), 107–8.

KGW, vi, 364.1–5.

Kepler had earlier elaborated on the anima telluris and its luminous nature in his Ad Vitellionem paralipomena (1604); see Kepler Johannes , Optics: Paralipomena to Witelo and optical part of astronomy, transl. by William H. Donahue (Santa Fe, 2000), 39–41, and Lindberg David C. , “The genesis of Kepler's theory of light: Light metaphysics from Plotinius to Kepler”, Osiris, ii (1986), 5–42, pp. 30–33.

KGW, vi, 237.20–26, 266.33–37, 268.15–17.

Ibid., 270.23–32, 270.39–271.2.

Aiton E. J. , n. 81 in Kepler , The harmony of the world (ref. 27), 364. In the eighth chapter of the De stella nova (1606) Kepler accounted for the existence of animate phenomena beyond human comprehension by calling attention to natural occurrences that could be explained only by the presence of a formative faculty acting outside the realm of human rationality; see KGW, i, 185.14–186.3. The idea of spontaneous generation was found in Aristotle and was widespread throughout the Renaissance.

Ptolemy , Tetrabiblos , 34c; see KGW , vi, 243; KGW , vii, 479.10–12. Kepler adopted the original five Ptolemy had espoused, in additional to eight more. The aspect known as conjunction occurred when one planet obscured another along the circumference (0°), while that of opposition occurred when two planets were situated opposite one another (180°). The next aspect was that of quartile, produced when two planets marked off 90° along the arc of the circle. The final two aspects were known as trine and sextile, respectively formed by the displacement of two planets by 120° and 60°. Compelling evidence in the form of extensive weather observations had led Kepler to consider the eight additional aspects ranked in order of descending influence: Octile (45°), trioctile (135°), semisextile (30°), quincunx (150°), quintile (72°), tridecile (108°), biquintile(144°) and decile (36°). Each of these angular displacements corresponded to the measurement of a side of a constructible polygon inscribed in a circle. The potential influence of each configuration was a consequence of its geometrical properties as deduced by Kepler. For an explanation of these properties, see Field , Kepler's geometrical cosmology (ref. 1), 131–5.

According to Kepler's view, light rays originating from the Sun reflected off planetary surfaces, absorbing some sort of impression from the encounter, and arrived at the Earth instantaneously; see Kepler Johannes , Kepler's conversation with Galileo's Sidereal messenger, transl. by Rosen Edward (New York, 1965), 34.

KGW, vi, 273.40–274.8.

Ibid., 268.24–30, 272.16–22.

Ibid. , 274.9–19. In addition to Kepler's uncertainty about the sublunary soul's modus et medii receptionis, he struggled with the subjective nature of his data and the seemingly superfluous occurrence of influential aspects; see Field Judith V. , “Astrology in Kepler's cosmology”, in Astrology, science and society: Historical essays, ed. by Curry Patrick (Bury St Edmunds, 1987), 143–70, pp. 149–51.

“To understand Kepler”, Brackenridge Bruce J. contended, “is to understand his ‘circular soul’ or ‘soul circle’. The archetype of the circle, rooted deeply in the mind and in nature, provided Kepler with a fundamental unity, made manifest in geometry, music, and astrology, that was to achieve its fruition in his analysis of celestial movement. Even the elliptical orbits of his new astronomy did not destroy this essential celestial circularity; on the contrary, the ellipse was found to be the very feature necessary to preserve circularity”; see his “Kepler, elliptical orbits, and celestial circularity … Part I” (ref. 3), 117.

KGW, vi, 278.8–12; see also Kepler , Optics (ref. 32), 39–40.

KGW , vi, 279.21–24. In the first of three chapters of the De Stella nova devoted to the natural effects of the new star (chaps. 28–30), Kepler made mention of a monstrous birth and its probable cause. On 2/12 January 1606 Siamese twins joined at the thorax and sharing several significant features, including the same face, were born in Strasbourg. Kepler pointed out that the father of the twins was a carpenter accustomed in his practice to joining things together, and that the impression this made on the mental experiences of the pregnant mother likely led to the unusual amalgamation of the offspring; see KGW, i, 321.6–24.

KGW, vi, 280.30–41.

Envisaged by Aristotle and codified in Christian theology, free will largely determined its own outcome rather than that decreed by the Creator. For Kepler, celestial influences contributed to the activities of earthly beings but did not play a decisive role. For further analysis on Kepler's incorporation of free will in his astrology, see Evans R. J. W. , Rudolf II and his world: A study in intellectual history 1576–1612 (Oxford, 1973), 280, and Rabin , “Two Renaissance views of astrology” (ref. 2), 159.

KGW, vi, 280.8–11. As a young district mathematician in Graz in 1597, Kepler drew up his own birth chart and accompanied it with several folios' worth of interpretation; see KGW, xix, no. 7.30, 328–37. Numerous excerpts from this document appear in Max Caspar's biography Kepler, ed. and transl. by Hellman Doris C. (New York, 1993), 39–41.

Burtt , The metaphysical foundations of modern physical science (ref. 7), 58.

Ibid. , 59. The implications of this problem have also been hinted at by Eloy Rada García, who has treated it more in terms of the mingling of disparate subject matter; see his Introduction to Kepler , El secreto del universo (ref. 24), 17: “Kepler applied his knowledge of astronomy and mathematics to the making of his prognostica without ruling out the astral influences, of whose reality he did not have greater doubts, although he held all these [i.e., astronomy and mathematics] out to the possibility of codifying causally those astral influences. His astrological prognostica waver between the conviction that nature is one and therefore unified in operational interdependence and the conviction that no astrological law is a strict causal law, by which consequence he must rule out from the prognostica any form of certainty similar to those of the mathematical sciences.”