This paper discusses the debate on capital theory between Frank H. Knight and Friedrich A. Hayek, which took place in the 1930s. The central objective is to make a historical reconstitution of this controversy, trying to understand it in its own terms by summarizing the arguments of both participants and placing each of its component articles in the context of the current theoretical developments of these authors. Furthermore, it is identified the way both capital theories are influenced or influence the other positions defended by the authors in related themes, especially, the scope and method of economic science.