 Green’s functions, which are broadly applicable in physics, are quite naturally interpreted in causal terms, allowing us to represent the state at \((x, t)\) as sum of different disturbances as its causes. In fact, Green’s functions provide “a primary locus for causal claims within physics texts” (Smith 2013: 667). The causal significance of the Green function formalism has been challenged, however, by invoking a version of the time-asymmetry challenge. In the case of systems governed by the time-reversal invariant hyperbolic equations (such as the wave equation which can be derived from the Maxwell-Lorentz equations in classical electrodynamics) any state of a system can be represented either as a sum of “causal” or so-called retarded Green’s functions and a solution to an initial value problem of the homogenous, source-free equation \(\mathrm{LG}=0;\) or as a sum of “anti-causal” or advanced Green’s functions and a solution to a final value problem of the homogenous, source-free equation. Both representations are mathematically equivalent representations of one and the same state of the system. From this observation the time asymmetry challenge concludes that nothing in the mathematical formalism can legitimately distinguish between the different representations to single out one representation as the correct causal representation. Since interpreting both retarded and advanced representations causally is incompatible with the causal asymmetry, neither representation ought to be interpreted causally.