Systems are defined by Karl Ludwig von Bertalanffy as “sets of elements standing in interrelation”. Acknowledging that the definition may seem vague, von Bertalanffy argues that when the idea is mathematized using differential equations, novel properties can be adduced in systems in general and in more specialized applied situations. Although von Bertalanffy has quite concrete objects in mind, for instance “a galaxy, a dog, a cell, and an atom are real systems” [von Bertalanffy’s emphasis], he also recognized as systems those “conceptual systems such as logic, mathematics (but e.g. also including music) which essentially are symbolic constructs; with abstracted systems (science) as a subclass of the latter, i.e. conceptual systems corresponding with reality.” [von Bertalanffy’s emphasis] There is, it would seem, an immediate parallel between von Bertalanffy and Husserl in their recognition that thinking of parts and whole (Husserl) or elements and systems (von Bertalanffy) can refer to quite concrete objects as well as more essential rules. It is pretty clear though that whereas Husserl has more commitments to the ideal over the empirical von Bertalanffy’s emphasizes the converse.
Hierarchy theory is a component of this more general systems theory that is applied to understanding the “architecture” of complex systems. “Nature loves hierarchies”, Herbert Simon, the social scientists, who pointed out that natural objects can be seen as arranged like Chinese boxes, each level inside a progressively larger box. Herbert Simon recognizes four intertwining sequences: chemical, organismic, genetic, and human social organizations. This fourth hierarchy includes “the “programs” and other components called elementary information processes”. We might like to think of this as “mind”, but in this fourth hierarchy Simon also includes those programs which “have been occurring with growing in the artificial complex systems called digital computers.”
The tenets of hierarchy theory have been attractive to ecologists since observations of the nestedness of ecological levels, organisms, populations (of a single species), communities (of several species), ecosystems (the biotic community combined with the abiotic environment) and so on. This hierarchy in natural systems is referred to as the “level of organization” concept. Ecologists have proceeded with the assumption that subsystems on the same level can be studied without reference to one another. For instance, we might study prairies, making the assumption that we do not simultaneously have to include tropical rainforests in our investigation. This methodological assumption relies upon the supposed “near-decomposability” of all medium-number systems and is rooted in the observation that “most interactions in nature, between systems of all kind, decrease in strength with distance.” However, there are some dangers in simply conflating ecological hierarchy with “levels of organizations” concept since natural systems are comprised of more than just simple entities (organisms with clearly defined boundaries, biotic communities that are spatiotemporally reasonably well designed etc.). They are also comprised of more diffusely defined sets of processes, and, depending upon the research question, there is more than one “n-1” level that might be examined.