Complexity as a cause of unsustainability

May's seminal work in theoretical ecology demonstrated by example that a large dynamic system with a complex set of interactions between state variables does not necessarily maintain dynamic stability as it grows in size. It is shown that this result is related to one of wider generality, and that it lends force to Tainter's qualitative argument that increased complexity might be the cause of the collapse of past societies. This conclusion has particular significance as current economic forces are tending to expand the interconnectivity of modern engineering, communication and financial systems on an unprecedented scale. These systems often have identifiable scaling laws and the relevance of these laws to May's results is discussed. (c) 2007 Published by Elsevier B.V.