Freedom is always the freedom of dissenters.

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.

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

Freedom only for supporters of the government, only for the members of one party - however numerous they may be - is no freedom at all. Freedom is always and exclusively freedom for the one who thinks differently. Not because of any fanatical concept of 'justice' but because all that is instructive, wholesome and purifying in political freedom depends on this essential characteristic, and its effectiveness vanishes when 'freedom' becomes a special privilege.

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.

Marxism is a revolutionary worldview that must always struggle for new revelations.

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.