The fundamental purpose of the article is to analyse the concept of social capital from a critical perspective. After being introduced into the social sciences by the economics (Loury) and political science (Putnam), this concept has gained an high credit in the sociological research. From a theoretical point of view, a central question is whether or not this concept can make advances for the social theory, once compared with the traditional background of sociology. In this regard, the usual stress that has been laid on social relations as specific element of this concept signals a characteristic which is doubtless highly relevant from a sociological point of view, but which has not been elaborated and conceptualised through an innovative perspective in the theory of social capital. Moreover, one can also observe the fact that such an element (probably showing an original, economic and political interest in the sociological paradigms) is usually applied only to specific social phenomena, such as group solidarity, thus being expunged from other types of phenomena, such as money and power, which, once adequately analysed, are instead rooted in their own forms of social relations that is, in their own forms of social capital.