The thesis put forward in this paper is that Herbert A. Simon was a distinctive theoretician of decentralized decisional systems alternative to the market, from planning to organizations. This issue emerges from the convergence of four perspectives, each with a different role and influence on his intellectual life: administrative and organization theories, the bounded rationality approach, economic theory, and the epistemology of complex systems. Notwithstanding the changes over time in his scientific interests and methods, the conviction that planning and organizations as decentralized structures can often perform a coordinating function better than the market appears in both his juvenile and mature works.