Gottfried Wilhelm Leibniz was a German philosopher whose writings were an oblique yet important influence on the New England Transcendentalists. His most significant philosophical work was
Monadology, in which he argued that all existing substances--as well as the human soul--are examples of monads acting in "pre-established harmony."
Ralph Waldo Emerson,
Georg Wilhelm Friedrich Hegel,
Johann Wolfgang von Goethe, and
W. T. Harris all appreciated Leibniz and adopted his concepts in one way or another.