Freedom for supporters of the government only, for members of one party only no matter how big its membership may be is no freedom at all. Freedom is always freedom for the man who thinks differently.

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.

[Geology] opens up such wide intellectual vistas and supplies a more perfectly unified and more comprehensive conception of nature than any other science.

We will be victorious if we have not forgotten how to learn.

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

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.

On the one hand, we have the mass; on the other, its historic goal, located outside of existing society. On one hand, we have the day-to-day struggle; on the other, the social revolution. It follows that this movement can best advance by tacking betwixt and between the two dangers by which it is constantly being threatened. One is the loss of its mass character; the other, the abandonment of its goal. One is the danger of sinking back to the condition of a sect; the other, the danger of becoming a movement of bourgeois social reform.