Kepler's Early Physical-Astrological Problematic

This paper is a fraction of a larger project whose working title is: “The Copernican question: Prognostication, scepticism and celestial order.” It covers the period from Copernicus's student days in Cracow and Bologna in the 1490s and ends around 1610 with Kepler's New astronomy and Galileo's presentation of his telescopic discoveries. Hereafter cited as The Copernican question.

See, for example, Gingerich Owen , “Johannes Kepler and the New Astronomy”, Quarterly journal of the Royal Astronomical Society, xiii (1972), 346–60, reprinted in Gingerich Owen , The eye of heaven (New York, 1993), 305–22, pp. 308–9; and, more recently, Stephenson Bruce , Kepler's physical astronomy (Princeton, 1994; first pub. 1987).

Kepler Johannes , “Fragmentum orationis de motu Terrae”, Gesammelte Werke, xx/1, 147–9; Voelkel James R. , “The development and reception of Kepler's physical astronomy, 1593–1609”, Ph.D. Dissertation, Indiana University, 1994, pp. 12–23 [a revised version is forthcoming as The composition of the Astronomia nova: The context and content of Kepler's New astronomy (Princeton, in press)].

Burtt E. A. , The metaphysical foundations of modern science (New York, 1924; 2nd rev. edn, 1932), 58–59: “the exalted position of the Sun in the new system appears as the main and sufficient reason for its adoption”.

Kuhn T. S. , Structure of scientific revolutions (Chicago, 1962; 2nd edn, 1970), 152–3.

This is a theme with which I was concerned long ago in “Kepler's adoption of the Copernican hypothesis”, Ph.D. dissertation, University of Michigan, 1971.

See Paulsen Friedrich , The German universities and university study, transl. by Thilly Frank and Elwang William (New York, 1906), 24–25. On the development of the institution of the academic disputation, see Clark William , “On the dialectical origins of the research seminar”, History of science, xxvii (1989), 111–54, esp. pp. 115, 145.

See Caspar Max , Kepler, transl. by Hellman Doris C. with additional material by Owen Gingerich and Alain Segonds (New York, 1993), 44.

For Liebler, see Methuen Charlotte , Kepler's Tübingen: Stimulus to a theological mathematics (Aldershot, 1998), 193–7, 203, 221–2, 226.

Müller taught ethics, 1592–1626, ibid., 227.

Kepler Johannes , Mysterium cosmographicum, “Preface to the Reader” (Gesammelte Werke, i, 9: “ut non tantùm crebrò eius placita in physicis disputationibus candidatorum defenderem: Sed etiam accuratam disputationem de motu primo, quòd Terrae volutione accidat”; my italics).

Segonds Alain points out that, in his Epitome astronomiae, Maestlin defined efficient and final causes as foreign to astronomy: “efficientis et finalis causae tanquam ab Astronomia alienae nulla fit mentio” (cited in Kepler Johannes , Le secret du monde, transl. with notes by Segonds Alain (Paris, 1984), 232n.). Yet, of course, Maestlin followed the generally accepted notion that astronomy contained a mathematical and a physical part.

The profound impression that Scaliger made upon the young Kepler is attested by an extensive group of notes that he added to the 1621 edition of the Mysterium, the first one of which was affixed to the first word in the book's title, Prodromus (= Precursor): “When I began my studies of philosophy in 1589 at the age of 18, the Exercitationes exotericae of Julius C[aesar] Scaliger was found in the hands of the young. One after another, I took the opportunity offered by this book to think about a variety of things on a variety of questions, such as on the heaven, souls, demons, elements, the nature of fire, the origin of springs, the ebb and flow of the sea, the shape of the Earth's continents and the seas that separate them, etc.” (Gesammelte Werke, viii, 15; see Segonds's further useful commentary on this passage, op. cit. (ref. 12), 238–9).

Kepler Johannes , Epitome astronomiae copernicanae. Gesammelte Werke , vii, Book iv, Part 2, 294; Epitome of Copernican astronomy, transl. by Wallis Glenn Charles (Great Books of the Western World, 16; Chicago, 1952; first publ., 1939), 891: “As a matter of fact, the professed Christian Scaliger and also the other followers of Aristotle dispute as to whether this motion of the orbs is voluntary and as to whether understanding and desire are the source of the will in the movers…. Furthermore, moving souls were added, tightly bound to the orbs and informing them, in order that they might assist the intelligences somewhat; or because it seemed necessary for the first mover and the movable [body] to unite in some third thing; or because the power [to cause] motion was finite with respect to the space to be traversed and the movement was not of an infinite speed but was described in a time measured out according to space: And, by this argument, the ratio of the moving power to the movable body and to the spaces was fixed and measured.” Here and elsewhere, I have modified Wallis's translation.

British Library: Shelf no. C.61.c.6. For the Tycho-Maestlin dedication see Westman Robert S. , “The comet and the cosmos: Kepler, Mästlin and the Copernican hypothesis”, in The reception of Copernicus' heliocentric theory , ed. by Dobrzycki Jerzy (Warsaw and Wroclaw, 1972; Boston, Dordrecht, 1972), Plate 2; also Gingerich Owen and Westman Robert S. , The Wittich Connection: Priority and conflict in late sixteenth-century cosmology, Transactions of the American Philosophical Society, lxxviii, no. 7 (1988), 60.

Kepler , op. cit. (ref. 14), 294; Kepler, transl. Wallis (ref. 14), 892: “For Aristotle will readily grant that a body cannot be transported by its soul from place to place, if the orb lacks the organ which reaches out through the whole circuit to be traversed, and if there is no immobile body upon which the sphere may rest. Moreover, even if we grant solid orbs, nevertheless there are vast intervals between the orbs. Either these intervals will be filled by useless orbs which contribute nothing to the state of movement — which is most absurd; or else, if there are no solid orbs throughout these intervals, then the spheres will not touch one another or carry one another”.

Kepler , op. cit. (ref. 14), 294; Kepler , transl. Wallis (ref. 14), 891.

Kepler's reasoning in a crucial passage of the Mysterium is a further evolution of the position adumbrated in the 1593 disputation (brackets refer to the notes that he added in 1621): “But if, nevertheless, we wish to get closer to the truth, and to find some regularity in the proportions, then one of two conclusions must hold: Either it is necessary that [note 2] the moving souls are weaker the further they are from the Sun; or [note 3] that there is one moving soul placed at the centre of all the orbs, that is, in the Sun, which vigorously incites a body to motion the closer that it is to it; but in those bodies furthest removed, because of their remoteness and the weakening of the [moving] virtue, it becomes fainter. Therefore, just as the source of light is in the Sun and the origin of the circle is in the place of the Sun, that is in the centre, so too life, motion and the world soul belong to that same Sun….” Kepler's 1621 note to this passage confirms both that Scaliger shaped the problematic of his earlier thinking and that by the later date, he felt no constraint in publicly acknowledging his earlier adherence to Scaliger's position: “For once I believed absolutely that the cause which moves the planets was a soul, as I was of course imbued with the teachings of J. C. Scaliger on moving Intelligences. But when I reflected that this moving cause grows weaker with distance, and that the Sun's light also weakens with distance from the Sun, from that I concluded, that this force is something corporeal, if not in an exact sense then at least in an equivocal sense, that is, when we say that light is something corporeal, that is to say, a species that originates from a body, but which is immaterial” (Kepler, Gesammelte Werke, viii, chap. 20, 113; transl. Segonds (ref. 12), 137–8, 140–1; cf. Kepler Johannes , Mysterium cosmographicum — The secret of the universe, transl. by Duncan A. M. with introduction and commentary by E. J. Aiton (New York, 1981), 203).

As Bruce Stephenson aptly notes, “The solid-sphere models had long coexisted with mathematical astronomy. They were compatible with the geometrical models for the very direct reason that they too were geometrical models”, op. cit. (ref. 2), 26.

“Jean Pic de la Mirandole et Johannes Kepler: De la mathématique à la physique”, Rinascimento, 2nd ser., xxxvi (1996), 275–96; for his Keplerian passages, Valcke draws liberally from Gérard Simon (Kepler, astronome-astrologue (Paris, 1979)) and also, Rabin Sheila (“Two Renaissance views of astrology: Pico and Kepler”, Ph.D. Dissertation, City University of New York, 1987).

Westman Robert S. , “Copernicus and the Bologna culture of prognostication, 1496–1500”, chap. 2, The Copernican question. For a very brief, early statement of this thesis see my “Copernicus and the prognosticators: The Bologna period, 1496–1500”, Universitas, no. 5 (December, 1993), 1–5.

Mirandola Pico della Giovanni , Disputationes adverus astrologiam divinatricem (Bologna, 1495), Book VI, chap. 4.

“For nature is a perpetuall circulatory worker, generating fluids out of solids, and solids out of fluids, fixed things out of volatile, & volatile out of fixed, subtile out of gross, gross out of subtile…” (quoted in B. J. T. Dobbs, The foundations of Newton's alchemy or “The Hunting of the Greene Lyon” (Cambridge, 1975), 206).

I believe that Pico's source in this passage is Ficino rather than Aristotle, as Valcke claims, op. cit. (ref. 20), 291n. More generally, see Barker Peter , “Stoic contributions to early modern science”, Atoms, pneuma and tranquillity: Epicurean and Stoic themes in European thought, ed. by Osler Margaret J. (Cambridge, 1991), 135–54.

Valcke , op. cit. (ref. 20), 291–3.

Bowden Ellen Mary , “The Scientific Revolution in astrology: The English reformers, 1558–1686”, Ph.D. Dissertation, Yale University, 1974; Field Judith , “A Lutheran astrologer: Johannes Kepler”, Archive for history of exact sciences, xxxi (1984), 189–272; Rabin Sheila , “Kepler's attitude toward Pico and the anti-astrology polemic”, Renaissance quarterly, 1 (1997), 750–70; Grafton Anthony , Commerce with the Classics: Ancient books and Renaissance readers (Ann Arbor, 1997), 123–5. Simon in Kepler, astronome-astrologue (ref. 20) wrote an extremely important account of Kepler's astrology but with surprisingly little attention to Pico.

Quoted and transl. in Rabin , op. cit. (ref. 26), 754; Kepler Johannes , Gesammelte Werke, iv, 161. I have slightly emended Rabin's translation.

This is precisely the trope that Kepler invokes in the title to his Tertius interveniens, a polemic with the Piconian Philip Feselius: Third Man in the Middle, that is, a warning to certain theologians, physicians and philosophers, and especially to Philip Feselius, that in their just condemnation of the star-gazing superstition, they should not throw out the baby with the bath water and in this way unwittingly harm their profession (Gesammelte Werke, iv, 147). For fuller discussion of this work, see Rabin , op. cit. (ref. 26), 143–98.

A group of books once owned by Maestlin are extant in the Stadtbibliothek Schaffhausen, including, most famously, his heavily annotated copy of Copernicus's De revolutionibus. Some 20% are books that Kepler sent to him and there is also a copy of Galileo's Sidereus nuncius with the 1633 provenance of Maestlin's son, Gottfried; but unfortunately one does not find Pico's Disputationes in this collection.

I discuss this matter in The Copernican question, chap. 9: “The second generation Copernicans: Maestlin and Digges.” So far as I know, Richard Jarrell was the first to call attention to Maestlin's opposition to astrology, although without establishing the connection to Pico that I am arguing for (“The life and scientific work of the Tübingen astronomer Michael Maestlin, 1550–1631”, Ph.D. Dissertation, University of Toronto, 1972), 138–40, 166, 176.

In the Narratio prima, Rheticus maintained that “Pico would have had no opportunity, in his eighth and ninth books, of impugning not merely astrology but also astronomy if he had known Copernicus's teachings”. To this passage Maestlin affixed a reader's postil showing that he knew the full name intended: “Picus Mirandola” (Johannes Kepler, Gesammelte Werke, i, 94).

Liebler Georg , Epitome philosophiae naturalis (Basel, 1561, 1566, 1573, 1575, 1581, 1589).

See Methuen , op. cit. (ref. 9), 196.

For Melanchthon's rejection of Pico, see, inter alia, Corpus Reformatorum, ed. by Bretschneider C. G. , v (Halle, 1838; repr. New York, 1963), 819.

This passage occurs under the question: “Of what substance are the stars [made]?”: “Mouetur autem coelum non ut calefaciat, sed ut uires suas astra cum subiectis partibus, alijs communicent pro materiae recipientis habilitate. Nee uerum esse arbitror, quod Mirandulanus libro aduersus Astrologos tertio contenait, Coeli praeter communem luminis et motus influentiam nullam peculiarem uim esse: Sed coelesti quidem calore haec inferiora uiuificari et vegetari: Frigus autem et siccitatem ex accidente fieri. Videmus enim hybemos quosdam dies admodum calidos, et contra aestiuos valde frigidos: Quod fieri non posse existimo, nisi astris quibusdam peculiaris aliqua uis inesset, hisce qualitatibus inferiora haec corpora afficiendi. Vires autem illas astrorum à proprijs ipsorum formis prouenire arbitor…” (Epitome philosophiae naturalis, 1573 edition, 224). The identical passage appears in the 1589 edition on pp. 234–6 (see Methuen , op. cit. (ref. 9), 195 n. 101); it appears likely that the argument was already present in the first edition, but I have been unable to confirm it.

I discuss Kepler's attempt to establish heliocentric foundations for astrology in The Copernican question, chap. 13: “Galileo and Kepler's Copernican problematic”.

As James Voelkel aptly puts it, “Kepler introduced motive power into his period-distance function”, op. cit. (ref. 3), chap. 2; on light and the virtus motrix, see Lindberg David C. , “Kepler's theory of light: Light metaphysics from Plotnius to Kepler”, Osiris, 2nd ser., ii (1986), 5–42, esp. pp. 38–39.

No later than the end of 1601, Kepler had worked out the elements of a reply to Piconian scepticism in his De fundamentis astrologiae certioribus (Prague, [1601]; Field , op. cit. (ref. 26)), although he would not take on Pico publicly until the De Stella nova in 1606 (Gesammelte Werke, i, 172–97).

See, for example, ref. 28.