This paper aims to clarify the controversial concept of “weight of argument” as introduced by Keynes in the Treatise of Probabilities and explicitly resumed in crucial passages of the General Theory (GT), in order to assess its influence on the theoretical framework and methodological approach of the GT. To this end the paper carries on a preliminary examination whether, and for what reason, we should expect that the weight of argument has a significant impact on economic decisions. A few recent development in epistemology and decision theory under uncertainty have reopened the issue, providing at the same time new analytical instruments capable to translate Keynes’s intuitions in rigorous and operational instruments. We suggest an interpretation of the concept of weight of argument that we believe consistent with the spirit of Keynes’s approach and that vindicates its substantial correctness and analytical potential in the light of the recent advances in decision theory under hard uncertainty. This interpretation confirms the practical relevance of the concept getting over the doubts expressed by Keynes himself, as well as its crucial role as a foundation of the theoretical and policy message of Keynes. It is thus possible and opportune to resume the research programme, suggested by Keynes with some timidity, meant to analyze the role of the weight of argument in economic decisions.
