"Nicholas of Cusa (1401-1464) was a German cardinal, philosopher, and administrator. For many years he served as papal legate to popes Eugene IV, Nicholas V, and Pius II. In addition to leading an extremely active public life, Nicholas managed to write extensively on a wide variety of juridicial, theological, philosophical, and scientific subjects. In his philosophical writings he departed from the prevalent Aristotelian and scholastic doctrines. His first and most famous treatise, On Learned Ignorance (De docta ignorantia), is a mystical discourse on the finite and the infinite. In addition to presenting his important philosophical concepts of learned ignorance and coincidence of opposites, this seminal treatise also contains various bold astronomical and cosmological speculations that depart entirely from traditional doctrines. For example, long before Copernicus, he proposed that the earth is not at the center of the cosmos, and is not at rest. He also argued long before Kepler that the motions of the planets are not circular. These speculations, however, were not based on empirical observations but on metaphysical principles."