Economic theory as a means for converting a concept into a project. The case (of the liberal variant) of basic income[La théorie économique comme outil de conversion d'une idée en projet. Le cas (de la version libérale) du revenu de base]

Debates among Liberals on social justice have played a major role in current discussion on basic income (or universal benefit). In this paper, the notion is based on the "economics of liberal egalitarianism", for which the anchor point is to be found in the hierarchy of Rawls' principles of justice (I). At the third level of this hierarchy, the interpretation of the "principle of difference" appeared controversial concerning the treatment of "Malibu surfers", through which Van Parijs can have defended the unconditional nature of basic income (II). There remains the transition from the philosophy to the economics of basic income, which allows considering it as a precise alternative of negative income tax. At this stage, a rereading of Friedman's intuition on this topic results in seeing basic income as a "universal tax credit" (III). From this case study, we sketch some remarks about the essential role of economic theory (more precisely, the role of a theory combining taxation and redistribution), so as to convert a concept, which is mainly of philosophical origin, into a viable project, which might eventually be applied (IV).