The idea for the operator hierarchy originates from an ecotoxicology study. This study aimed at integrating different aspects of soil ecotoxicology acros many levels of natural organization. I was convinced the reaching of such a goal required a clear picture of the levels everyone used. It was fascinating to see that the literature offered a hodgepodge of elements and hierarchy rules. The operator hierarchy can be regarded as an attompt to bring clarity on this point.
The operator hierarchy originates from 1992. It started with the question how to organize toxicant targets in organisms? I decided to take an evolutionary approach, because every step in the evolution of organisms endows the system with new properties. These new properties represent equally many new targets for change. A transparent ranking of organism properties would therefore offer a structured ranking of targets.
Upon trying to answer the latter question, I realized that the organization type of organisms differs from that of ecosystems. Organismal organization results from subsequent construction steps (e.g. from bacteria to eukaryotes, from unicellular to multicellular). These construction steps always involve circularity, or 'closure'.
The use of closure allowed the identification of a much larger construction sequence, including the quarks, the hadrons, the atom nucleus, the atom, the molecule, the prokaryote cell, the eukaryote cell, the multicellular organisms and the multicellular organisms with neural network. I have given this sequence the name of the 'operator hierarchy'.