Market theory must be able to describe through a price mechanism the decentralized and competitive coordination of individual plans for the provision of resources, very often but not exclusively associated with the notion of equilibrium, as well as a market process where exchanges lead the economy to this state. Its power is to consider that a market society where all individuals pursue their own well-being can favorably organize itself through the free functioning of the market for all those who intervene without falling into chaos (Arrow and Hahn 1971: vii). Thus, market theory is placed at the historic and logical base of economics, so this is the only inescapable challenge to the economist. This explains what attracted the attention of almost all schools of economic thought since Adam Smith (Ibid.: vi-vii).