Marxism is the opium of the Marxists.

Rosa Luxemburg maintained that the capitalist system can keep up its rate of investment (and therefore its profits) only so long as it is expanding geographically.

In all the talk in the Principles (as opposed to the formal analysis) it is not the saving of rentiers but the energy of entrepreneurs which governs accumulation.

The very nature of economics is rooted in nationalism. ... It [was] developed ... in the hope of throwing light upon questions of policy. But policy means nothing unless there is an authority to carry it out, and authorities are national.

Capital' is not what capital is called, it is what its name is called.

Progress is slow partly from mere intellectual inertia. In a subject where there is no agreed procedure for knocking out errors, doctrines have a long life. A professor teaches what he was taught, and his pupils, with a proper respect and reverence for teachers, set up a resistance against his critics for no other reason than that it was he whose pupils they were.

Income from property is not the reward of waiting, it is the reward of employing a good stockbroker.