The late Howard T. Odum (1924-2002), the renowned American ecologist and systems analyst, viewed thermodynamic constraints as limiting the development of self-organizing biological organisms. In work with his then colleague Richard C. Pinkerton in the mid-1950s he devised the so-called 'maximum power and optimum efficiency' axiom for ecology. This led to a means for analysing the energetics of systems more generally with the notion of EMERGY, or 'energy memory', at its core. This rightly allowed for differences in the quality of energy sources, although the practical application of the property has had its critics over time. Later in his life, Odum was concerned with the need for human society to embrace a new ethics and set of policies for the 'descent' away from a growth path in order to ensure 'a prosperous way down' for this complex world modelled on the pulsing paradigm in nature. Here, Odum's ideas are critically assessed from outside his own circle in terms of insights gleaned from the use of engineering thermodynamics (energy and exergy analysis) and environmental appraisal methods, as well as those provided by the modern paradigm of 'sustainability'. This contribution forms part of a sequence of papers in which the author and his collaborators have re-evaluated the use of thermodynamic ideas outside their traditional domain of energy systems. These have encompassed the use of Second Law concepts for resource and/or emissions accounting and, more recently, in ecological economics. It was argued that in these earlier cases the use of such ideas outside the realm of energy systems implies a weak analogy or metaphor. rather than representing thermodynamic limits in a physical sense. The present work also employs the results of environmental, or 'ecological', footprinting at a global and national scale to judge where humanity stands on the pathway towards sustainability. Copyright (C) 2007 John Wiley & Sons, Ltd.