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

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.

Those who don't move don't notice their chains.

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.

We stand todaybefore the awful proposition: either the triumph of imperialism and the destruction of all culture, and, as in ancient Rome, depopulation, desolation, degeneration, a vast cemetery; or, the victory of socialism.

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.

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