Y-a-t-il des lois naturelles en économie ? Histoire et portée du concept de "taux de chômage naturel"

The aim of the paper is to analyse the theme of the conference in a specific way, by probing the question of the existence of natural laws in economics. This very general question in tackled here by studying the epistemological, analytical and practical significances of the concept of a "natural" rate of unemployment. For that purpose, the paper explores two directions :- the first part comes under the historical direction suggested in the call of papers. It consists in reconsidering the history and the topicality of the concept worked out by Friedman. This is the occasion to underline the limits of the analogy asserted by Friedman between his own theory of the "natural rate of unemployment" and Wicksell's theory of the "natural rate of interest", and, as a result, to highlight the divergence between the two, in the representations they have of monetary economy, money and monetary policies. In the line of these developments, it is also the occasion to underline the shifts that Friedman, using a form of "authoritative argument", introduces in to the contents of the macroeconomic debate.- the second part comes under the "epistemological" direction of the call of papers. It questions the significance of the reference to the concept of a "natural rate of unemployment", endeavouring to draw a parallel between the criticism of the concept of the "naturality" of unemployment, conveyed in particular by works about the hysteresis of equilibrium rates of unemployment, and the criticism by Sraffa (1932) of the concept, worked out by Wicksell and taken up again by Hayek, of a "natural rate of interest".As a conclusion, the paper examines the normative significance of the reference to the "naturality" of economic law.