  Indefinite causal structure is generically present in theories of quantum
gravity admitting a path integral formulation. We show that summing over causal
structures eliminates ultraviolet divergences of matter QFT and resolves
spacetime singularities using the non-perturbative World Quantum Gravity
approach. Independent information-theoretic and model-independent
considerations suggest that the mechanism of ultraviolet regularization by
indefinite causal structure also applies to other theories of quantum gravity.
