Corliss Lamont was a humanist philosopher and civil liberties advocate. He was born in Englewood, New Jersey to Thomas W. Lamont, a Partner and later Chairman at J.P. Morgan & Co.. Lamont graduated as valedictorian of Phillips Exeter Academy in 1920, and magna cum laude from Harvard University in 1924. In 1924 he did graduate work at New College University of Oxford, while he resided with Julian Huxley.

The next year Lamont matriculated at Columbia University, where he studied under John Dewey. In 1928 he became a philosophy instructor at Columbia and married Margaret Hayes Irish. He received his Ph.D. in 1932. Dr. Lamont taught at Columbia, Cornell, Harvard, and the New School for Social Research (see New School University).

Lamont's political views were socialist. During the 1930s he was sympathetic to Soviet communism, but never joined the Communist Party, and later came to reject his earlier views. In 1953 he published a pamphlet entitled Why I am not a Communist.

A leading proponent of civil rights, he served as a director of the American Civil Liberties Union from 1932 to 1954, and subsequently as chairman until his death, of the National Emergency Civil Liberties Committee, which successfully challenged Senator Joseph McCarthy's senate subcommittee and other government agencies. In 1965 he secured a Supreme Court ruling against censorship of incoming mail by the U.S. Postmaster General.

In 1973 he discovered through Freedom of Information Act requests that the FBI had been tapping his phone, and scrutinizing his tax returns and cancelled checks for 30 years. His subsequent lawsuit showed the surveillance had no justification in law, and set precedent for other citizens' privacy rights. He also filed and won a suit against the Central Intelligence Agency for opening his mail.

Lamont wrote sixteen books, hundreds of pamphlets and thousands of letters to newspapers on significant social issues during his life long campaign for peace and civil rights. His most famous book is probably The Philosophy of Humanism, which is considered the definitive study of the humanist philosophy. Another contribution to the field was the 1935 book The Illusion of Immortality, which was a revised version of his Ph.D. dissertation. He also published intimate portraits of such luminaries as John Dewey and Bertrand Russell.

Following the deaths of his parents Lamont became a philanthropist. He funded the collection and preservation of manuscripts of American philosophers, particularly George Santayana. He became a substantial donor to both Harvard and Columbia. During the 1960s he and Margaret had divorced, and he married author Helen Boyden, who died of cancer in 1975. Lamont married Beth Keehner in 1986 and they shared their mutual interests for the remainder of his life.

Lamont was president emeritus of the American Humanist Association and received the Gandhi Peace Award in 1981. In 1998 Lamont received a posthumous Distinguished Humanist Service Award from the International Humanist and Ethical Union.

He remained a peace activist all his life, protesting U.S. involvement in the Persian Gulf War at the age of 88. He died at home in Ossining, New York.