E. Hutchinson, who thought that if a community were an organism then it must have a form of metabolism. However, Golley notes that Odum attempted to go beyond the reporting of mere ratios, a move which resulted in the first serious disagreement in systems energetics. Maximum power theory and the proposal for additional laws of thermodynamics/energetics In a controversial move, Odum and Richard Pinkerton (at the time physicist at the University of Florida) were motivated by Alfred J. Lotka's articles on the energetics of evolution, and subsequently proposed the theory that natural systems tend to operate at an efficiency that produces the maximum power output, not the maximum efficiency. Energy Systems Language By the end of the 1960s, Odum's electronic circuit ecological simulation models were replaced by a more general set of energy symbols. When combined to form systems diagrams, these symbols were considered by Odum and others to be the language of the macroscope which could portray generalized patterns of energy flow: "Describing such patterns and reducing ecosystem complexities to flows of energy, Odum believed, would permit discovery of general ecosystem principles." Some have attempted to link it with the universal scientific language projects which have appeared throughout the history of natural philosophy. Kitching claimed that the language was a direct result of working with analogue computers, and reflected an electrical engineer's approach to the problem of system representation: "Because of its electrical analogy, the Odum system is relatively easy to turn into mathematical equations ... If one is building a model of energy flow then certainly the Odum system should be given serious consideration... " Emergy In the 1990s in the latter part of his career, Odum and David M. Scienceman developed the idea of emergy as a specific use of the term embodied energy. Some consider the concept of "emergy", sometimes briefly defined as "energy memory", as one of Odum's more significant contributions, but the concept is neither free from controversy nor without its critics. Odum looked at natural systems as being formed by the use of various forms of energy in the past: "emergy is a measure of energy used in the past and thus is different from a measure of energy now. The unit of emergy (past available energy use) is the emjoule, as distinguished from joules used for available energy remaining now." This was conceived as a principle of maximum empower, which might explain