… is from page 112 of Joseph Schumpeter‘s much-praised – but still-not-praised-enough – 1942 book, Capitalism, Socialism, and Democracy:
There is surely no such gulf between Marx and Keynes as there was between Marx and Marshall or Wicksell. Both the Marxist doctrine and its non-Marxist counterpart are well expressed by the self-explanatory phrase that we shall use: the theory of vanishing investment opportunity.
