This volume offers a new interpretation of Marx's great work. It shows how the novelty and lasting interest of Marx's theory arises from the fact that, as against the project of a `pure' economics, it is formulated in concepts that have simultaneously an economic and a political aspect, neither of these being separable from the other. Jacques Bidet conducts an unprecedented investigation of Marx's work in the spirit of the history of science, exploring it as a process of theoretical development.