One can in particular interpret the proposition as a statement conditi — Tjalling Koopmans

"We look upon economic theory as a sequence of conceptual models that seek to express in simplified form different aspects of an always more complicated reality."

"… a rather different class of applications of the idea of best allocation of scarce resources... usually referred to as the theory of optimal economic growth. In most studies of this kind made in the countries with market economies there is not an identifiable client to whom the findings are submitted as policy recommendations. Nor is there an obvious choice of objective function, such as cost minimization or profit maximization in the studies addressed to individual enterprises. The field has more of a speculative character. The models studied usually contain only a few highly aggregated variables. One considers alternative objective functions that incorporate or emphasize various strands of ethical, political, or social thought. These objectives are then tried out to see what future paths of the economy they imply under equally simplified assumptions of technology or resource availability."

"The principal customers aimed for are other economists or members of other professions, who are somewhat closer to the making of policy recommendations... The question of the clientèle is even more baffling when the problem concerns growth paths for time spans covering several generations. What can at best be recommended in that case is the signal the present generation gives, the tradition it seeks to strengthen or establish, for succeeding generations to take off from."

"The early thirties brought what liberal economists called the Great Depression and Marxist economists described as the great crisis of capitalism. It dawned on me that the economic world order was unreliable, unstable, and, most of all, iniquitous. I sought intellectual contacts and friendship with a group of socialist students and also with a small handful of communist-oriented students and unemployed workers."

"It is worth pointing out that in this particular study our authors have abandoned demand and supply functions as a tool for analysis, even as applied to individuals... [The problem] has been reformulated as one of proving that a number of maximizations of individual goals under interdependent restraints can be simultaneously carried out."

"Optimizing responses of economic agents are simultaneously feasible only if the proper prices are already known to them. But these prices must somehow themselves be the result of the same responses."