What is novel about modern rationalism is its increasingly insistent claim that it has discovered the principle which connects up all phenomena which in nature and society are found to confront mankind. Compared with this, every previous type of rationalism is no more than a partial system. (HCC, The Antinomies of Bourgeois Thought)

Lukacs distinguishes between other kinds of systems in addition to the (ir)rational. The idea of “total” and “partial” systems also plays an important role in his analysis. I think the following tentative definitions reflect his use of the terms fairly well:

(DFN-TOTAL-SYSTEM-v.1.0) A total system is a system that connects up all phenomena.

(DFN-PARTIAL-SYSTEM-v.1.0) A partial system is a system that is not a total system, in the sense of (DFN-TOTAL-SYSTEM-v.1.0).

We have also discussed before, without adding a definition to our list, the concept of a closed system. We can try to sketch this out here:

(DFN-CLOSED-SYSTEM-v.1.0) A closed system is a system whose content does not depend on any variables exogenous to it.