@JLNobody,
The theorizer necessarily
attempts to stand aloof from "the system". Therefore there is a least
one "thing" outside the system, hence the theory can never encompass "everything".
This mirrors Godel's "incompleteness theorem" in which all formal systems require at least one axiom which cannot be deduced from the system itself.
All we can hope for is a potential infinite regress of nested observations of observation, any of which might be functional in"explaining"(i.e predicting) events at a "lower" level. But ultimately "events" must always be relative to "observers", and "prediction" will be relative to "time" for that observer.
The transcendent position from which these comments ensue, is one of zero differention between observer and observed, and the consequent deconstruction of "measurement of change" which provides the time dimension along which "prediction" operates. With respect to that, the word "theory" becomes meaningless, but the
epistemological appreciation of that in no way detracts from possible technological progress.