Preestablished Harmony Revisited: Generalised Entanglement is a Modern Version of Preestablished Harmony

Leibniz' notion of "pre-established harmony" is one of the central notions of his philosophy. It is the conceptual hinge which allows all monads to be interrelated and coordinated yet not influenced by each other through causal interactions, allowing Leibniz to construct a model of the world where moral justice can be philosophically incorporated. This concept has been viewed with some misgivings during the history of philosophy, finally being dismantled during the post-modern turn. We suggest its revival, based on the concept of a weak or generalised quantum theory, an axiomatic, systems theoretical approach, modelled along the same lines as the algebraic quantum theory. In contrast to quantum theory this drops a lot of definitions and restrictions, and is also applicable to different types of systems. Interestingly, its formalism preserves one central element of the quantum mechanical formalism: the handling of non-commuting or complementary observables. In consequence, the model predicts a generalised form of entanglement, i.e. non-local correlations across distance and time, that are not mediated through signals, but through the make up of the system as such. This seems to be a "mechanism" or coordination which could operate independent of and complementary to standard causal interactions, akin to the way Leibniz conceived pre-established harmony. We argue that such a generalised version of entanglement (GET) is in fact a systematic novel interpretation of pre-established harmony. If this line or argument is prolonged into the realm of morality and ethics, we have in fact a full fledged revival of Leibniz pre-established harmony.