Entanglement phenomena can generally be characterised as phenomena where the behaviour and properties of parts of a complex whole cannot be described and understood independently from the behaviour of the other parts and of the complex as such. The probably best-known instance of this is quantum entanglement, which is one of the phenomena of the greatest philosophical interest in quantum mechanics. In quantum entanglement, there are states of composite systems (a pair of particles, say) that cannot be "factorised'' into separate states for the component subsystems (i.e. of the particles considered in isolation). In such a case, it seems natural to say that "the whole is more than the sum of its parts''. But the philosophical challenge is to provide a precise characterisation of this metaphorical idea, which is compatible with plausible general metaphysical theories. Various such characterisations have been offered for the case of quantum entanglement: Perhaps the particles are tied together by some novel class of relations; perhaps there are not really two distinct particles at all, and the whole (rather than its parts) should be considered as fundamental; perhaps it is a mistake to think of the world as made of separate objects at all.

In attempting to understand entanglement phenomena, we are working closely together with our sister project on Power Structuralism, and are trying to apply the insights of that metaphysical approach and of a robust realism about potentialities to the explanation of these phenomena. We believe that in doing so, we will be able to develop fruitful new strategies to account for entanglement phenomena, and, at the same time, be able to locate the explanation of these phenomena in a promising general metaphysical framework.