Why are things as they are and not otherwise?

As soon as somebody demonstrates the art of flying, settlers from our species of man will not be lacking on the moon and Jupiter... Given ships or sails adapted to the breezes of heaven, there will be those who will not shrink from even that vast expanse.

Nature uses as little as possible of anything.

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

Astronomy would not provide me with bread if men did not entertain hopes of reading the future in the heavens.

So, Fabricius, I already have this: that the most true path of the planet [Mars] is an ellipse, which Dürer also calls an oval, or certainly so close to an ellipse that the difference is insensible.

If this [the Mysterium cosmographicum] is published, others will perhaps make discoveries I might have reserved for myself. But we are all ephemeral creatures (and none more so than I). I have, therefore, for the Glory of God, who wants to be recognized from the book of Nature, that these things may be published as quickly as possible. The more others build on my work the happier I shall be.