Bolshevism is not merely a political doctrine; it is also a religion, with elaborate dogmas and inspired scriptures. When Lenin wishes to prove some proposition, he does so, if possible, by quoting texts from Marx and Engels. A full-fledged Communist is not merely a man who believes that land and capital should be held in common, and their produce distributed as nearly equally as possible. He is a man who entertains a number of elaborate and dogmatic beliefs—such as philosophic materialism, for example—which may be true, but are not, to a scientific temper, capable of being known to be true with any certainty. This habit, of militant certainty about objectively doubtful matters, is one from which, since the Renaissance, the world has been gradually emerging, into that temper of constructive and fruitful scepticism which constitutes the scientific outlook. I believe the scientific outlook to be immeasurably important to the human race. If a more just economic system were only attainable by closing men’s minds against free inquiry, and plunging them back into the intellectual prison of the middle ages, I should consider the price too high.

Bertrand Russell, The Practice and Theory of Bolshevism, London, 1920, p. 8