Bolshevism is to be reckoned with Mohammedanism rather than with Christianity and Buddhism. Christianity and Buddhism are primarily personal religions, with mystical doctrines and a love of contemplation. Mohammedanism and Bolshevism are practical, social, unspiritual, concerned to win the empire of the world.

The Collected Papers of Bertrand Russell: Uncertain Paths to Freedom: Russia and China, 1919-22. v. 28. Man's Peril, 1954-55 (ed. 2000)