The basic proposition of this paper is that the so-called "new economic sociology", which is rooted in key ideas of Karl Polanyi, is an indispensable "tool" for two tasks: a) it provides us with a powerful critique of market fundamentalism, and b) it allows us to analyze the economic performance of contemporary capitalism by accessing the working of its institutional structure. From an analytical perspective, the paper suggests that Polanyian Economic Sociology is an essential complement to both the Schumpeterian and the Post-Keynesian perspectives in economics. This is especially so when it comes to the discussion of "socioeconomic stability" and, more precisely, as Keynes himself stated in the General Theory: to explain why capitalist economies manifest themselves in different ways and degrees, in spite of encompassing inherent elements of instability and unpredictability.