Making changes represents abandoning the known, but our brain resists the unknown. It interprets a danger to survival, that is the reason why change is not so simple. The Great Crisis of the 1930s undoubtedly marked a before and after in economic theory. The world went into a very deep crisis, the levels of unemployment and marginalization spread everywhere, and the mechanisms of market adjustment that previously worked, now seemed not to work. At that time reigned in the academic world the theories of classic and neoclassical, as A. Smith, D. Ricardo, A. Marshall, S. Jevons, among others, and very few dared to discuss them. The neoclassicals always argued full employment for all factors of production, arguing that if the economy was slow to reach its equilibrium, it was because of the existence of unfortunate government interventions or by monopoly powers (also the fault of the state), which prevented the correct functioning of the competition. And while these theories were l...