Money as a mechanism to intersubjectively compare entirely subjective preferences

This article contributes a money model that allows to interpersonally compare the entirely subjective material preferences of different economic subjects. It rests on a graph-based model for the network of economic relevant interactions, taking into account the dependence between the nodes (subjects) and the edges (interactions) with a role concept. We apply our model to the two complementary roles of buyer and seller, which externally compose to a trade and internally to a trader. We prove a simple utility representation to be the only one that is 'compositionally consistent' for both compositions. In this money model, interpersonal comparison of subjective material preferences is possible if (1) the decisions of an economic subject can be modeled by a preference model where preferences are expressible as utility. And (2) all buyers have the same total budget and the same access to the same set of alternatives. Equipping the seller with a discretionary component, as is the case in the employment relationship, then a hierarchically superior notion of fairness on his part leads to a recursive determination of utility with the price fixed point of the buyer's valuation.