As Quoted in "The Discovery of Kepler's Laws," Scientific American: Supplement (Apr 29, 1911) Vol. 71, No. 1843, p. 278 https://books.google.com/books?id=ov4-AQAAMAAJ&pg=PA258. <br class="br">Mysterium Cosmographicum (1596)

“The earth is the sphere, the measure of all; round it describe a dodecahedron; the sphere including this will be Mars. Round Mars describe a tetrahedron; the sphere including this will be Jupiter. Describe a cube round Jupiter; the sphere including this will be Saturn. Now, inscribe in the earth an icosahedron, the sphere inscribed in it will be Venus: inscribe an octahedron in Venus: the circle inscribed in it will be Mercury.”

Johannes Kepler book Mysterium Cosmographicum

Walter William Bryant, Kepler (1920), pp. 16–17
Mysterium Cosmographicum (1596)

“If the earth should cease to attract its waters to itself all the waters of the sea would be raised and would flow to the body of the moon.”

Johannes Kepler book Astronomia nova

As quoted by Bryant, ibid.
Astronomia nova (1609)

“Without proper experiments I conclude nothing.”

Johannes Kepler

Vol. V. p. 224, Vol. I, p. 143
Joannis Kepleri Astronomi Opera Omnia, ed. Christian Frisch (1858)

“[Quantity is the fundamental feature of things, ] the primarium accidens substantiae,' …prior to the other categories.”

Johannes Kepler

Vol. VIII, p. 150
Joannis Kepleri Astronomi Opera Omnia, ed. Christian Frisch (1858)

“Nature uses as little as possible of anything.”

Johannes Kepler

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

“The heavenly bodies are nothing but a continuous song for several voices (perceived by the intellect, not by the ear); a music which… sets landmarks in the immeasurable flow of time. It is therefore, no longer surprising that man, in imitation of his creator, has at last discovered the art of figured song, which was unknown to the ancients. Man wanted to reproduce the continuity of cosmic time… to obtain a sample test of the delight of the Divine Creator in His works, and to partake of his joy by making music in the imitation of God.”

Johannes Kepler book Harmonices Mundi

Book V, Ch. 7 as quoted in Arthur Koestler, The Sleepwalkers (1959)
Harmonices Mundi (1618)

“But although the attractive virtue of the earth extends upwards, as has been said, so very far, yet if any stone should be at a distance great enough to become sensible compared with the earth’s diameter, it is true that on the motion of the earth such a stone would not follow altogether; its own force of resistance would be combined with the attractive force of the earth, and thus it would extricate itself in some degree from the motion of the earth.”

Johannes Kepler book Astronomia nova

As quoted by Bryant, ibid.
Astronomia nova (1609)

“There are, in fact, as I began to say above, not a few principles which are the special property of mathematics, such principles as are discovered by the common light of nature, require no demonstration, and which concern quantities primarily; then they are applied to other things, so far as the latter have something in common with quantities. Now there are more of these principles in mathematics than in the other theoretical sciences because of that very characteristic of the human understanding which seems to be such from the law of creation, that nothing can be known completely except quantities or by quantities. And so it happens that the conclusions of mathematics are most certain and indubitable.”

Johannes Kepler

Vol. VIII, p. 148
Joannis Kepleri Astronomi Opera Omnia, ed. Christian Frisch (1858)

“There is a force in the earth which causes the moon to move.”
In Terra inest virtus, quae Lunam del.

Johannes Kepler

Essay dedicated to the Archduke Ferdinand, as quoted in Kepler (1993) by Max Caspar, Sect. II, Ch. 9, p. 110

“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.”

Johannes Kepler

Translation by an unknown person, from De fundamentis astrologiae certioribus, ibid., from the foreword

Ref: en.wikiquote.org - Johannes Kepler / Mysterium Cosmographicum (1596) / De fundamentis astrologiae certioribus (1601)