One way to evaluate and compare rival but potentially incompatible theories that account for the same set of observations is coherence. In this paper we take the quantitative notion of theory coherence as proposed by [Kwok, et.al. 98] and broaden its foundations. The generalisation will give a measure of the efficacy of a sub–theory as against single theory components. This also gives rise to notions of dependencies and couplings to account for how theory components interact with each other. Secondly we wish to capture the fact that not all components within a theory are of equal importance. To do this we assign weights to theory components. This framework is applied to game theory and the performance of a coherentist player is investigated within the iterated Prisoner’s Dilemma.