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• Discover the force of the heavens O Men: once recognised it can be put to use.
  • De Fundamentis [On the more Certain Fundamentals of Astrology or On Giving Astrology Sounder Foundations] (1601)

• He who will please the crowd and for the sake of the most ephemeral renown will either proclaim those things which nature does not display or even will publish genuine miracles of nature without regard to deeper causes is a spiritually corrupt person… With the best of intentions I publicly speak to the crowd (which is eager for things new) on the subject of what is to come.
  • De Fundamentis (1601)

• Nature uses as little as possible of anything.
  • Viking Book of Aphorisms: A Personal Selection (1920) by W. H. Auden and Louis Kronenberger, p. 98; also in The Infinite Cosmos: Questions from the Frontiers of Cosmology (2006) by Joseph Silk

• We do not ask for what useful purpose the birds do sing, for song is their pleasure since they were created for singing. Similarly, we ought not to ask why the human mind troubles to fathom the secrets of the heavens. The diversity of the phenomena of nature is so great and the treasures hidden in the heavens so rich precisely in order that the human mind shall never be lacking in fresh nourishment.
  • As quoted in Cosmos (1980) by Carl Sagan.

• In Terra inest virtus, quae Lunam del.
  • There is a force in the earth which causes the moon to move.
    • Essay dedicated to the Archduke Ferdinand, as quoted in Kepler (1993) by Max Caspar, Sect. II, Ch. 9, p. 110

• Geometry has two great treasures; one is the Theorem of Pythagoras; the other, the division of a line into extreme and mean ratio. The first we may compare to a measure of gold; the second we may name a precious jewel.
  • As quoted in The Golden Ratio : The Story of Phi, the World's Most Astonishing Number (2003) by Mario Livio, p. 62

• I much prefer the sharpest criticism of a single intelligent man to the thoughtless approval of the masses.
  • As quoted in (K)new Words: Redefine Your Communication (2005) by Gloria Pierre, p. 147

• I used to measure the heavens, now I measure the shadows of Earth.
  Although my mind was heaven-bound, the shadow of my body lies here.
  • Epitaph he composed for himself a few months before he died, as quoted in Calculus. Multivariable (2006) by Steven G. Krantz and Brian E. Blank. p. 126
  • Unsourced variant: I used to measure the Heavens, now I measure the shadows of Earth. The mind belonged to Heaven, the body's shadow lies here.

• Temporis filia veritas; cui me obstetrcari non pudet.
  • Truth is the daughter of time, and I feel no shame in being her midwife.
  • As quoted in The Ismailis in the Middle Ages : A History of Survival, A search for Salvation (2007) by Shafique N. Virani, p. 28

Harmonices Mundi (1618)

Translated asThe Harmonies of Worlds or The Harmony of the World

• Geometry is one and eternal shining in the mind of God. That share in it accorded to humans is one of the reasons that humanity is the image of God.
  • Book III, Ch. 1 as quoted in "Astrology in Kepler's Cosmology" by Judith V. Field, in Astrology, Science, and Society: Historical Essays (1987) edited by P. Curry, p. 154
  • Geometry, coeternal with God and shining in the divine Mind, gave God the pattern... by which he laid out the world so that it might be best and most beautiful and finally most like the Creator.
    • As quoted in Kepler's Geometrical Cosmology (1988), p. 123
  • Geometry is one and eternal shining in the mind of God. That share in it accorded to men is one of the reasons that Man is the image of God.
    • Unsourced variant

• Since geometry is co-eternal with the divine mind before the birth of things, God himself served as his own model in creating the world (for what is their in God which is not God?), and he with his own image reached down to humanity.
  • Book IV, Ch. 1, as quoted in "Kepler's Astrology"in Kepler, Four Hundred Years (1975) edited by Arthur and Peter Beer.

• If you want the exact moment in time, it was conceived mentally on 8th March in this year one thousand six hundred and eighteen, but submitted to calculation in an unlucky way, and therefore rejected as false, and finally returning on the 15th of May and adopting a new line of attack, stormed the darkness of my mind. So strong was the support from the combination of my labour of seventeen years on the observations of Brahe and the present study, which conspired together, that at first I believed I was dreaming, and assuming my conclusion among my basic premises. But it is absolutely certain and exact that "the proportion between the periodic times of any two planets is precisely the sesquialterate proportion of their mean distances..."
  • Stating the dates that his Third Law of Planetary Motion occurred to him, in Book 5, Ch. 3, as translated by E J Aiton, A M Duncan, and J V Field, p. 411
  • A fresh assault overcame the darkness of my reason...
    • As quoted in Calculus. Multivariable (2006) by Steven G. Krantz and Brian E. Blank. p. 126

• Now because 18 months ago the first dawn, 3 months ago broad daylight but a very few days ago the full sun of the most highly remarkable spectacle has risen — nothing holds me back. I can give myself up to the sacred frenzy, I can have the insolence to make a full confession to mortal men that I have stolen the golden vessel of the Egyptians to make from them a tabernacle for my God far from the confines of the land of Egypt. If you forgive me I shall rejoice; if you are angry, I shall bear it; I am indeed casting the die and writing the book, either for my contemporaries or for posterity to read, it matters not which: let the book await its reader for a hundred years; God himself has waited six thousand years for his work to be seen.
  • Book 5
  • Variant translations: It may well wait a century for a reader, as God has waited six thousand years for an observer.
    • As quoted in The Martyrs of Science; or, the Lives of Galileo, Tycho Brahe, and Kepler (1841) by David Brewster, p. 197. This has sometimes been misquoted as "It may be well to wait a century for a reader, as God has waited six thousand years for an observer."
  • I feel carried away and possessed by an unutterable rapture over the divine spectacle of heavenly harmony... I write a book for the present time, or for posterity. It is all the same to me. It may wait a hundred years for its readers, as God has also waited six thousand years for an onlooker.
    • As quoted in Calculus. Multivariable (2006) by Steven G. Krantz and Brian E. Blank. p. 126
  • I am stealing the golden vessels of the Egyptians to build a tabernacle to my God from them, far far away from the boundaries of Egypt. If you forgive me, I shall rejoice.; if you are enraged with me, I shall bear it. See, I cast the die, and I write the book. Whether it is to be read by the people of the present or of the future makes no difference: let it await its reader for a hundred years, if God himself has stood ready for six thousand years for one to study him.
    • Unsourced translation

• The soul of the newly born baby is marked for life by the pattern of the stars at the moment it comes into the world, unconsciously remembers it, and remains sensitive to the return of configurations of a similar kind.

• But who shall dwell in these worlds if they be inhabited?....Are we or they Lords of the World?....And how are all things made for man?(War of the Worlds by HG Wells)

Quotes about Kepler

• As living bodies have hair, so does the earth have grass and trees, the cicadas being its dandruff; as living creatures secrete urine in a bladder, so do the mountains make springs; sulphur and volcanic products correspond to excrement, metals and rainwater to blood and sweat; the sea water is the earth's nourishment ... At the same time the anima terrae [soul of the earth] is also a formative power (facultas formatrix) in the earth's interior and expresses, for example, the five regular bodies in precious stones and fossils ..... It is important that in Kepler's view the anima terrae is responsible for the weather and also for meteoric phenomena. Too much rain, for instance, is an illness of the earth.
  • Wolfgang Pauli in "The Influence of Archetypal Ideas on the Scientific Theories of Kepler" in The Interpretation of Nature and the Psyche (1955) by Carl Jung and Wolfgang Pauli, as translated by Priscilla Silz

• One wonders how many modern scientists faced by a similar situation in their work would fail to be impressed by such remarkable numerical coincidences.
  • Fred Hoyle on Kepler's attention to the apparent harmonics by which he deduced his planetary laws, as quoted in "Kepler's Astrology and Mysticism" by A. Beer in Vistas in Astronomy vol. 18 (1975).

• Kepler was a brilliant thinker and a lucid writer, but he was a disaster as a classroom teacher. He mumbled. He digressed. He was at times utterly incomprehensible. He drew only a handful of students his first year at Graz; the next year there were none. He was distracted by an incessant interior clamour of associations and speculations vying for his attention. And one pleasant summer afternoon, deep in the interstices of one of his interminable lectures, he was visited by a revelation that was to alter radically the future of astronomy. Perhaps he stopped in mid-sentence. His inattentive students, longing for the end of the day, took little notice, I suspect, of the historic moment.
  • Carl Sagan in Cosmos (1980)

• A law explains a set of observations; a theory explains a set of laws. The quintessential illustration of this jump in level is the way in which Newton’s theory of mechanics explained Kepler’s law of planetary motion. Basically, a law applies to observed phenomena in one domain (e.g., planetary bodies and their movements), while a theory is intended to unify phenomena in many domains. Thus, Newton’s theory of mechanics explained not only Kepler’s laws, but also Galileo’s findings about the motion of balls rolling down an inclined plane, as well as the pattern of oceanic tides. Unlike laws, theories often postulate unobservable objects as part of their explanatory mechanism. So, for instance, Freud’s theory of mind relies upon the unobservable ego, superego, and id, and in modern physics we have theories of elementary particles that postulate various types of quarks, all of which have yet to be observed.
  • John L. Casti in "Correlations, Causes, and Chance," Searching for Certainty: How Scientists Predict the Future (1990).