The author proposes a method to arrive at a cardinal theory of utility or welfare (considered identical) by the introduction into the utility function of (1) variables, (2) parameters and (3) coefficients. Parameters characterize measured differences between individuals relevant to the problem considered; variables indicate either choices open to individuals (job, income) or exogenous circumstances (a salary scale or a tax scale). The ethical postulate introduced is the equality of each coefficient among different individuals, offered as an interpretation of the fundamental equality of men. Once the utility function has been defined and tested, justice in distribution is defined as equality of the values of that function for all individuals considered. A numerical illustration is added in which years of schooling and degree of independence are used as parameters to characterize twenty social groups and the just as distinct from the actual income distribution is calculated for the Netherlands around 1965. It affords the Board of Editors great pleasure to publish this paper by one of their members. This gives the Board the opportunity, also on behalf of the readers ofDe Economist, to congratulate Professor Tinbergen most cordially upon his 70th birthday, which he celebrated on 12th April, 1973.