"Diversity of opinions on theoretical points is never dangerous to the party. There are for us no bounds to criticism, and however great our respect may be for the founders and pioneers of our party, we recognize no infallibility and no other authority than science, whose sphere is ever widening and continually proves what it previously held as truths to be errors; destroys the old decayed foundations and creates new ones; does not stand still for an instant; but in perpetual advance moves remorselessly over every dogmatic belief."

“What is it that has made of us in Germany the pivotal part? ... It is the avalanche-like increase of our supporters that gradually, with the certainty of a natural law, or more correctly of a natural force, grows from tens of thousands to hundreds of thousands, and from hundreds of thousands to millions, and is daily increasing, bidding defiance to our opponents and driving them into impotent rage. And this avalanche-like increase has come, and is coming, as a consequence of our opposition to and struggle with all other parties.”

“It would be an unparalleled case of flying the track and going astray if the German Social Democracy, which has had such wonderful success and such a wonderful growth for the very reason that it has marched ahead unterrified on the basis of the class struggle, should suddenly face about and plunge into mistakes, the avoidance of which has been the power and pride of our party, and has put the German Social Democracy at the head of the international social democracy of all countries.”

“We Social Democrats dare not be like the other parties, all of whom are equally guilty of the injustices of the present system and equally responsible for them. Every one who suffers under these injustices looks to us for deliverance. Every one of us has had these victims of society after failing to get justice from the courts, from the government, from the Emperor himself, and from all the other parties, come to us as the last and only ones that can help them. They do not know our scientific program; they do not know what capital and capitalism mean; but they have the belief, the feeling, that we are a party that can help when all other parties fail. This belief is for us an inexhaustible source of power. It was a similar faith of despair that spread more and more in the decaying Roman empire and slowly undermined the heathen world until it finally collapsed. We give up this inexhaustible source of power if we ally ourselves with other parties and drive suffering humanity from us by saying to it: “We are not essentially different from the others.” Once the boundary line of the class struggle is wiped away and we have started upon the inclined plane of compromise, there is no stopping. Then we can only go down and down until there is nothing deeper.”

“We cannot traffic in our principles, we can make no compromise, no agreement with the ruling system. We must break with the ruling system and fight it to a finish. It must fall that socialism may arise, and we certainly cannot expect from the ruling class that it will give to itself and its domination the death blow.”

“Distrust was counted as a democratic virtue, and over-confidence as a democratic vice.”

“The highest triumph of Bismarckian politics carried its downfall and bankruptcy within it.”