Became involved in revolutionary activity and Marxist propaganda, exiled to Vologda, 1898. Went to Germany to study, and returned to Petersburg in 1904. Co-editor with Bulgakov of the philosophical magazin Voprosy zhizni.
Became widely known as a representative of a group of thinkers who moved from Marxism towards a religious view of life. Gained the reputation of a philosopher of freedom, which he considered to be the pre-condition of all true existence. Stressed the value of personality and individual liberty.
His philosophy is defined as personalism or Christian existentialism. His popularity was greatly increased by his colourful, aphoristic style, which gave little regard to logical development of thought. He himself considered his non-academic approach to philosophy a definite virtue.
Taught at the private Academy of Spiritual Culture in Moscow, 1918-1922. Exiled after an interview with Dzerzhinskii, 1922 (together with a large group of intellectuals sent abroad by Lenin). Went to Berlin. Settled in France, near Paris, 1925.
Married L. Rapp. Very active in the emigre press as author, editor and organizer (one of the founders of the YMCA Press in Paris, which published most of the Russian thinkers living abroad after 1917). Became widely known in the 1930s, and remains the best known modern Russian philosopher in the West. Under the influence of the events of World War II, took a pro-Soviet line, and after the war took a Soviet passport, but did not return to the USSR. Received an Oxford doctorate in 1947.