The solution of important problems may be delayed because the requisit — Tjalling Koopmans

"[This work urges] a clearer separation, in the construction of economic knowledge, between reasoning and recognition of facts, for the better protection of both."

"If evolutionary selection is the basis for a belief in profit maximization, then we should postulate that basis itself and not the profit maximization which it implies in certain circumstances."

"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."

"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."

"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."

"… 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."