Fyodor Mikhailovich Dostoevsky (November 11 [O.S. October 30] 1821 - February 9 [O.S. January 28] 1881) is considered one of two greatest prose writers of Russian literature, alongside close contemporary Leo Tolstoy. Dostoevsky's works have had a profound and lasting effect on twentieth-century thought and world literature. Dostoevsky's chief ouevre, mainly novels, explore the human psychology in the disturbing political, social and spiritual context of his 19th-century Russian society. Considered by many as a founder or precursor of 20th-century existentialism, his Notes from Underground (1864), written in the anonymous, embittered voice of the Underground Man, is considered by Walter Kaufmann as the "best overture for existentialism ever written."