The working classes in every country only learn to fight in the course of their struggles.

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.

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.

The existing legal constitution is nothing but the product of a revolution. Revolution is the act of political creation in the history of classes, while constitutional legislation is the expression of the continual political vegetation of a society.

History is the only true teacher, the revolution the best school for the proletariat.