The nature of energy and material resources in an endogenous growththeory framework is clarified. This involves three modifications of the conventional theory. Firstly, multiple feedback mechanisms or "growth engines" are identified. Secondly, a productionfunction distinguishesbetween resource...

Standard economic theory regards capital and labour as the main factors of production that satisfy the “cost-share theorem”. This paper argues that when a third factor, namely energy, is added physical constraints on substitution among the factors arise. We show that energy is a much more...