The book’s closing Chapter 9 on change in economics begins with an examination of the methodological problem of explaining what counts as change, and argues change in economics needs to be explained in terms of economics’ relationships to other disciplines. It argues that economics’ core–periphery structure works to insulate its core from other disciplines’ influences upon it, minimizing their influences. This raises the question: Can other disciplines influence economics’ core and potentially produce change in economics? To investigate this question, the chapter develops an open–closed systems model of disciplinary boundary crossings and argues that economics’ core is only incompletely closed and consequently its adopting other disciplines’ contents can change its interpretation. Using the different forms of relationships between disciplines distinguished in Chapter 7, mainstream economics’ relations to other disciplines are argued to currently be interdisciplinarity, but may also be unstable and can break down. When and under what circumstances? Moving from what happens within social science, two sets of external forces influencing change in economics – change in how research is done and historical changes in social values and social expectations regarding what economics is and should be about – are argued likely to increase boundary crossings between economics and other disciplines, undermine the insularity of its core, and move economics toward being a multidisciplinary, more pluralistic discipline. What would then be especially different about economics would be that individuals are seen as socially embedded and an objective economics is seen as a normative, value-entangled science.