The search for harmonic relationships in the natural world motivated Kepler's scientific investigations. Whether endeavoring to understand the structure of snowflakes and or seeking the principles that underlie the organization of the cosmos as a whole , Kepler saw congruencies in nature and between the human intellect and the material world as evidence of the goodness of God and signposts of man's divine potential.
Kepler wrote, "For the theater of the world is so ordered that there exist in it suitable signs by which human minds, likenesses of God, are not only invited to study the divine works, from which they may evaluate the founder's goodness, but are also assisted in inquiring more deeply." (Optics, p. 15)
Kepler's ideas about harmony, proportion, and the nature of knowledge can be more fully appreciated with reference to the work of the renaissance statesman and mathematician , Cardinal Nicholas of Cusa (1401-1464), whose influence may be glimpsed throughout the astronomer's work.