An example of untranslatability: the conceptual structures of Marshall's and Keynes' conceptions of investment *.

This essay discusses the following two hypotheses. The first one is based on the epistemological proposal which we have named the principle of discontinuity. It asserts that certain developments in the history of economic thought involve theoretical breaks which can only be fully explained by making use of the concept of discontinuity. The second hypothesis concerns one of the consequences drawn from the principle of discontinuity, namely, the untranslatability of concepts. Besides other theories to which reference is made by way of examples of specific conclusions regarding the principle of discontinuity, the conceptual structures of Marshall's and Keynes' conceptions of the determinants of investment are analysed and compared with the aim of illustrating the aforementioned hypotheses. [ABSTRACT FROM AUTHOR]