Arthur Schopenhauer was a German philosopher who wrote the influential work, The World as Will and Representation. His metaphysical analysis of will, his views on human motivation and desire, and his aphoristic writing style influenced many well-known thinkers including Friedrich Nietzsche, Richard Wagner, Ludwig Wittgenstein, Erwin Schrödinger, Albert Einstein, Sigmund Freud, Carl Gustav Jung, and Leo Tolstoy. 
The following is from an entry in the Stanford Encyclopedia of Philosophy:
"Within Schopenhauer's vision of the world as Will, there is no God to be comprehended, and the world is conceived of as being meaningless." 
From A History of God, by Karen Armstrong, ISBN 0345384563, p. 353:
"There was, Schopenhauer believed, no Absolute, no Reason, no God, no Spirit at work in the world: nothing but brute instinctive will to live."