ABSTRACT
In this chapter I discuss the social and economic ideas of an early contributor to equilibrium theory, the French engineer Achilles Nicolas Isnard (1748-1803), in the context of his overall scientific production. In this way, I show that Isnard developed sophisticated views about human decision-making processes. While he claimed that producers and consumers make decisions on the basis of personal interests, he qualified these as being supported by unreflective, impulsive or habitual, action and concluded that only conduct motivated by an ‘interested’ choice that is ‘fortified by virtuous habits’ leads to socially desirable outcomes. This concern with the motivations of humans engaging in social transactions stands in strong contrast with modern economic equilibrium theory.
