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Johannes Kepler on the Holy Work of Astronomy

Photo: Orion Nebula, by ESA/Hubble & NASA, J. Bally, M. Robberto.

Editor’s note: This article is adapted from the new book by Dr. Travis, Thinking God’s Thoughts: Johannes Kepler and the Miracle of Cosmic Comprehensibility.

The astronomer Johannes Kepler was convinced that by studying God’s book of nature, one’s worship of the Creator is vastly elevated. In a dedicatory letter at the beginning of the Mysterium Cosmographicum (1596) he asks, “Why then as Christians should we take any less delight in [nature’s] contemplation, since it is for us with true worship to honor God, to venerate him, to wonder at him? The more rightly we understand the nature and scope of what our God has founded, the more devoted the spirit in which that is done.”1

Pointing to the Creator

In the dedication to the first three books of his Epitome of Copernican Astronomy (1619) he writes, “I have been made priest of God, the creator of the book of nature. I have composed this hymn for God the creator.”2 That he saw astronomy as holy work is further illustrated by the closing prayer at the end of the Harmonice Mundi (1619), quoted here in full:

It now remains for me, at the very last, to take my eyes and hands away from the table of proofs, lift them up to the heaven, and pray devoutly and humbly to the Father of light: O Thou who by the light of Nature movest in us the desire for the light of grace, so that by it thou mayest bring us over into the light of glory; I thank Thee, Creator Lord, because Thou hast made me delight in Thy handiwork, and I  have exulted in the works of Thy hands. Lo, I have now brought to completion the work of my covenant, using all the power of the talents which Thou hast given me. I have made manifest the glory of Thy works to men who will read these demonstrations, as much as the deficiency of my mind has been able to grasp of its infinity. My intellect has been ready for the most accurate details of philosophy. If anything unworthy of Thy intentions has been put forward by me, miserable worm that I am, born and nourished in a slough of sins, which thou wouldst wish men to know, inspire me also to set it right; if I have been enticed into temerity by the wonderful splendor of Thy works, or if I have loved my own glory among men, while advancing in work destined for Thy glory, mildly and mercifully pardon it; and last, be gracious and deign to bring about that these my demonstrations may be conducive to Thy glory and to the salvation of souls, and may in no way obstruct it.3

The final line of Kepler’s prayer is indicative of the value he saw in his life’s work for the purposes of natural theology. Clearly, he believed that his work pointed beyond the material realm to a creator God.

Kepler rejected the idea that the enormous scale of the cosmos, or heliocentric cosmology, suggested that mankind is less important than in the cozier, geocentric Aristotelian-Ptolemaic model. In other words, he did not see relative size or geometric location as having any bearing on human significance in the grand scheme of the world. In a letter to Herwart von Hohenburg dated December 16, 1598, Kepler quotes Copernicus, who had declared, “So great indeed is the edifice of our Almighty and Allkind Creator,” and then adds that “we should feel less astonished at the huge and almost endless width of the heavens than at the smallness of us human beings, the smallness of this, our tiny ball of earth.”4

He goes on to say that man is “puny” compared with the universe, “Yet one must not infer from bigness to special importance” because if physical size indicates our significance in the eyes of the Creator, then (he quips) “the crocodile or the elephant would be closer to God’s heart than man, because these animals surpass the human being in size.”5 His statement directly implies that it is absurd to equate physical size with objective value or to think that our comparative smallness is indicative of a universe that is not metaphysically anthropocentric.

A Fortunate Location

As for the earth’s location in orbit around the central sun, Kepler regarded this arrangement as incredibly fortunate for the natural philosopher seeking to know God’s mind through its manifestation in the creation. Thus, the position of man’s home planet demonstrates his privileged status in the cosmic economy. In his commentary on Galileo’s Sidereus Nuncius, Kepler writes that man was created to contemplate the heavens, and that because he is 

adorned and equipped with eyes, he could not remain at rest in the center. On the contrary, he must make an annual journey on this boat, which is our earth, to perform his observations…There is no globe nobler or more suitable for man than the earth. For, in the first place, it is exactly in the middle of the principal globes… Above it are Mars, Jupiter, and Saturn. Within the embrace of its orbit run Venus and Mercury, while at the center the sun rotates.6

As historian Dennis Danielson points out, “This is clearly a complete reconceptualization of what it means to be in the center. To exercise or actualize their divine image properly, humans must be able to observe the universe from a ‘central’ but dynamic and changing point of view conveniently provided by what Kepler sees as this optimally placed orbiting space station of ours.”7 Kepler continues his argument about the earth’s location being best suited for the work of the astronomer: “We on the earth have difficulty in seeing Mercury, the last of the principal planets, on account of the nearby, overpowering brilliance of the sun. From Jupiter or Saturn, how much less distinct will Mercury be? Hence this globe seems assigned to man with the express intent of enabling him to view all the planets.”8

Kepler’s Humane Art

Historian Max Caspar offers additional pertinent details about Kepler’s view:

Was [the earth] humiliated by being pushed out of the center of the world? By no means…By its motion around the sun its inhabitants will be enabled to ascertain the size of the world. The unchanging inclination of the earth’s axis takes care of the change of seasons and brings about an equitable distribution of the sunshine on the inhabitants of the various zones…On this trip around the stationary sun, man can observe with understanding the wonder of the world in its diversity of phenomena. For everything is there because of man.9

Danielson sums it up well; he writes that for Kepler, “only with the abolition of geocentrism may we truly say that we occupy the best, most privileged place in the universe.”10 Truly, it seems that the Creator specifically intended the humane art of astronomy.


  1. Johannes Kepler, Mysterium Cosmographicum (Norwalk Connecticut: Opal Publishing, 1981), 53.
  2. Carola Baumgardt, Johannes Kepler: Life and Letters (New York: Philosophical Library Inc, 1951), 122–123.
  3. Johannes Kepler, The Harmony of the World (Philadelphia: American Philosophical Society, 1997), 491.
  4. Baumgardt, 48–49.
  5. Ibid., 49.
  6. Johannes Kepler, Kepler’s Conversation with Galileo’s Sidereal Messenger (Johnson Reprint Corp., 1965), 45.
  7. Dennis Danielson, “The great Copernican cliché,” American Journal of Physics 69 no. 10 (October 2001): 1032.
  8. Kepler, Kepler’s Conversation with Galileo’s Sidereal Messenger, 46.
  9. Max Caspar, Kepler (New York: Dover Publications, 1993), 386–387.
  10. Danielson, 1032. Kepler’s argument has been adopted and expanded in contemporary intelligent design literature.