Integration of knowledge has become a contentious issue in an age where increasing specialisation creates boundaries and division. Yet, there is an identifiable need for integration across social, ecological and economic understandings if we are to address ever more threatening crises and alarming potential scenarios. This paper relates to the work of K. William Kapp and in so doing raises questions about how integration might be achieved. A core idea that arises is the role of common denominator concepts. (author's abstract) / Series: SRE - Discussion Papers