O telescope, instrument of much knowledge, more precious than any sceptre!

The chief aim of all investigations of the external world should be to discover the rational order and harmony which has been imposed on it by God and which He revealed to us in the language of mathematics.

A most unfailing experience... of the excitement of sublunary (that is, human) natures by the conjunctions and aspects of the planets has instructed and compelled my unwilling belief.

As soon as somebody demonstrates the art of flying, settlers from our species of man will not be lacking on the Moon and Jupiter. Who would have believed that a huge ocean could be crossed more peacefully and safely than the the narrow expanse of the Adriatic, the Baltic Sea or the English Channel? Given ships or sails adapted to the breezes of heaven, there will be those who will not shrink from even that vast expanse.

The radius vector describes equal areas in equal times.

We do not ask what hope of gain makes a little bird warble, since we know that it takes delight in singing because it is for that very singing that the bird was made, so there is no need to ask why the human mind undertakes such toil in seeking out these secrets of the heavens. ... And just as other animals, and the human body, are sustained by food and drink, so the very spirit of Man, which is something distinct from Man, is nourished, is increased, and in a sense grows up on this diet of knowledge, and is more like the dead than the living if it is touched by no desire for these things.

I measured the skies, now the shadows I measure, Sky-bound was the mind, earth-bound the body rests. [Kepler's epitaph]