The authors Buchdahl, Callen, and Haase make no mention of the passage of radiation, thermal or coherent, across their adiabatic walls. Carathéodory explicitly discusses problems with respect to thermal radiation, which is incoherent, and he was probably unaware of the practical possibility of laser light, which is coherent. Carathéodory in 1909 says that he leaves such questions unanswered.