The book investigates the relationship between the economic and political writings of four seminal authors: Adam Smith, Karl Marx, Joseph A. Schumpeter, and John M. Keynes. It underlines how in their works the nexus between ethics, economics, and politics has produced four exemplary solutions. They represent the most relevant modern formulations of the idea of 'political interest', to which the philosophical and political debate constantly returns, as the thought of Carl Schmitt, Hannah Arendt, and Michel Foucault demonstrates. The author discusses the different interpretations by considering economic science not as a natural, but as moral and political science.