A depression is a situation of self-fulfilling pessimism.

Utility is a metaphysical concept of impregnable circularity; utility is the quality in commodities that makes individuals want to buy them, and the fact that individuals want to buy commodities shows that they have utility.

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.

In general, the nightmare quality of Marx's thought gives it, in this bedevilled age, an air of greater reality than the gentle complacency of the orthodox academics. Yet he, at the same time, is more encouraging than they, for he releases hope as well as terror from Pandora's box, while they preach only the gloomy doctrine that all is for the best in the best of all possible worlds.

But, as soon as speculators become an important influence in the market, their business is to speculate on each others behaviour.

New ideas are difficult just because they are new. Repetition has somehow plastered over the gaps and inconsistencies in the old ones, and the new cannot penetrate.

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.