 Notably, Evans, Price, &amp; Wharton (2013) argue that there is such an action symmetry between a pair of entangled photons passing through separate polarizers and a single photon passing sequentially through two polarizers. Thus, if action duality is well-founded, the action symmetry should be reflected in identical ontologies for the action-dual experiments. Short of rejecting action duality, this implies one of two things: either the usual causal explanation for the behavior of the single photon must be reflected in a causal explanation for the typically-quantum behavior of the pair of entangled photons, and so there must be retrocausality at the level of the ontic state \(\lambda\), or the nonlocality ascribed to the typically-quantum behavior of the pair of entangled photons must be similarly ascribed to the behavior of the single photon, and so nonlocality is even more dramatically widespread than usually assumed, and indeed is not unique to entangled bipartite quantum systems. In so far as there is a strong case for the behavior of a single photon passing sequentially through two polarizers having a perfectly good causal explanation based on spatiotemporally localized properties, the argument of Evans et al. is that this amounts to an equally strong case for retrocausality in quantum theory.