In the context of the equilibrium of the productive class, the fundamental principle of reciprocal utility in exchange requires that three conditions be satisfied: ‘proportionate prices’, the ‘tacit condition’ of exchange and free competition. I have suggested that according to Boisguilbert the third condition implies the other two; this suggestion will now to be examined in detail. The unresolved problem of the relationship between the social group approach and the aggregated markets approach must also be broached. In the considerations which follow, we shall return to the question – partially left aside until now – of the precise position of the leisure class both within society and in regard to the achievement of economic equilibrium.