One day, a serious, brutal crisis devastated the world economy: factories closed, unemployment exploded, houses were mortgaged, their inhabitants thrown onto the roads and banks stopped lending to those who needed it most. We then spoke of going beyond the market, of moralizing the liberal economy, of inventing an alternative humanist future. There was even talk of a return of Marxism. Finally Keynes appeared and the mixed economy of which he established himself as the theoretician breathed a second life into the capitalist system, at the same time contradicting Marx's predictions. But wasn't this system destined to come up against historical limits again, another day? To this essential question, Paul Mattick (1904, Berlin - 1981, Boston), activist and theoretician of the revolutionary and anti-Stalinist German left, refusing the dictatorship of the centralized party in favor of worker self-organization through elected councils, devoted this work which deals with fundamental problems - the accumulation of capital, money, automation, underdevelopment, state capitalism, etc. From the confrontation between Keynes and Marx, he concludes that many of the latter's analyzes are still linked to the future, our future.