A sure sign of a crisis is the prevalence of cranks. It is characteristic of a crisis in theory that cranks get a hearing from the public which orthodoxy is failing to satisfy.

owning capital is not a productive activity.

I do not regard the Keynesian revolution as a great intellectual triumph. On the contrary, it was a tragedy because it came so late. Hitler had already found out how to cure unemployment before Keynes had finished explaining why it occured.

Ideology is like breath: you never smell your own.

The point of studying economics is so as not to be fooled by economists.

Marxism is the opium of the Marxists.

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.