By employing the concept of a social capital the author argues that the best measure of a theoretical development for any economic theory of organisation is its contribution in the understanding of a social capital. In this way social capital is becoming one of the key factors of evolutionary changes within the economic theory of organisation. The author further wishes to point out how the evolutionary progress in economic theory of organisation brings about increasingly improved understanding of the relations in the theoretical models. However, the concession required for this improvement is a lower degree of a theoretical generalisation and more intense heterogeneity of the economic theory itself. The less effort an economic theory of organisation devotes to being theoretically impeccable, the more abundant are the increasing returns it yields through its findings with regard to the aspect of the social capital.