Peter Checkland on Ontology

“Systems is an epistemology (making a statement of the kind: 'A certain type of knowledge may be expressed in systems language') before it is an ontology (which would make a statement of the kind: 'The world is systemic'); and in the case of work whose concern is social reality it may never be possible to make ontological statements in systems terms.”

“A sample of the modern debate, which neatly summarizes the anti-reductionist position is provided by Grene (1974). She points out that in principle a one-level ontology—the belief, for example, that with increasing knowledge all science will become an account of the world in the language of, say, atomic events—contradicts itself. This is so because such a belief, to be meaningful, requires an ontology which admits both atomic events and cognition. Here at once a second level is smuggled in! It is logically possible... that there might be no levels in between those of atomic events and cognition (that in essence is Descartes's position) but the sciences of chemistry and biology consist of some well-tested conjectures that there are such intermediate levels as are represented by molecules, cells, organelles, organs, and organisms.”