Marxism must abhor nothing so much as the possibility that it becomes congealed in its current form. It is at its best when butting heads in self-criticism, and in historical thunder and lightning, it retains its strength.

Only through the conscious action of the working masses in city and country can it be brought to life, only through the people's highest intellectual maturity and inexhaustible idealism can it be brought safely through all storms and find its way to port.

Being human means throwing your whole life on the scales of destiny when need be, all the while rejoicing in every sunny day and every beautiful cloud.

The working classes in every country only learn to fight in the course of their struggles...Social democracy...is only the advance guard of the proletariat, a small piece of the total working masses; blood from their blood, and flesh from their flesh. Social democracy seeks and finds the ways, and particular slogans, of the workers' struggle only in the course of the development of this struggle, and gains directions for the way forward through this struggle alone.

With the true artist, the social formula that he recommends is a matter of secondary importance; the source of his art, its animating spirit, is decisive.

Only to the rude ear of one who is quite indifferent does the song of a bird seem always the same.

Self-criticism, cruel, unsparing criticism that goes to the very root of the evil, is life and breath for the proletarian movement.