We are firmly convinced, that it is not practical experiments which are dangerous but the theoretical articulation of communist ideas; true practical experiments (and be they carried out en masse) can be answered by cannon as soon as they become dangerous; ideas, however, which control our thoughts, subordinate our convictions to them, and to which reason rivets our conscience—these are bonds impossible to break without tearing into pieces one’s heart, these are demons which a man can conquer only by subjecting himself to them.

— Karl Marx