Among 19th century philosophers, Arthur Schopenhauer was among the first to contend that at its core, the universe is not a rational place. Inspired by Plato and Kant, both of whom regarded the world as being more amenable to reason, Schopenhauer developed their philosophies into an instinct-recognizing and ultimately ascetic outlook, emphasizing that in the face of a world filled with endless strife, we ought to minimize our natural desires to achieve a more tranquil frame of mind and a disposition towards universal beneficence. Often considered to be a thoroughgoing pessimist, Schopenhauer in fact advocated ways — via artistic, moral and ascetic forms of awareness — to overcome a frustration-filled and fundamentally painful human condition. Since his death in 1860, his philosophy has had a special attraction for those who wonder about life's meaning, along with those engaged in music, literature, and the visual arts.
See more at http://plato.stanford.edu/entries/schopenhauer