Gottfried Wilhelm Leibniz was the greatest German philosopher of the seventeenth century and one of the greatest polymaths of all time. His philosophical position, a creative eclecticism of ancient and modern thought, has influenced all subsequent European philosophy. He made significant contributions to the full range of human knowledge, including mathematics, science, jurisprudence, history, poetry, bibliography, and etymology. Leibniz's learning was practical as well as theoretical. He was a valued counselor to emperor, king, and czar and worked indefatigably for the reconciliation of churches and for general social and political order in Europe. He invented a calculating machine, devised engineering projects, and catalogued major libraries. An entire academy in himself, as the French encyclopedist Denis Diderot styled him, Leibniz was the last great representative of the Renaissance encyclopedic ideal of combining learning with service to humanity. His personal motto, theoria cum praxi (theory with practice), summarizes what he...