Then what is it in our day to-day struggles that makes us a socialist party? It can only be the relation between these three practical struggles and our final goals. It is the final goal alone which constitutes the spirit and the content of our socialist struggle, which turns it into a class struggle. And by final goal we must not mean, as Heine has said, this or that image of the future state, but the prerequisite for any future society, namely the conquest of political power. [Shout: "Then we do agree!] This conception of our task is closely related to our conception of capitalist society; it is the solid ground which underlies our view that capitalist society is caught in insoluble contradictions which will ultimately necessitate an explosion, a collapse, at which point we will play the role of the banker-lawyer who liquidates a bankrupt company.
http://www.marxists.org/archive/luxemburg/1898/10/04.htm