INTRODUCfiON This book argues that realist theorizing in the discipline of International Relations can be understood as an ongoing, and repeatedly failed, attempt to translate the maxims of the European international society to the different context of the twentieth century. This translation of the sceptic and power-materialist world-view within which European diplomats used to be socialized had two main facets. First, realist theorists wanted to contain the practical idealist conceptions of international politics, prominent in the inter-war period but present also later, in particular in the US, the country which had to take on international leadership. Realism used the vehicle of 'scientific' presentation to persuade the new international diplomatic elite of the US. Second, since the academic discipline developed predominantly in the US, the academic group, in turn, needed to be isolated from those dispositions, typical of US empirical social sciences, which would water down the particularity of international politics. The independence of international expertise and the struggle against idealism, later against behaviouralism, are hence but two sides of the same endeavour.