Religious thought often assumes that the principle of physical causal completeness (PCC) is false. But those who explicitly deny or doubt PCC, including William Alston, W. D. Hart, Tim Crane, Paul Moser and David Yandell, Charles Taliaferro, Keith Yandell, Dallas Willard, William Vallicella, Frank Dilley, and, recently, David Chalmers, have ignored not only the explicit but also the implicit grounds for acceptance of PCC. I review the explicit grounds, and extend the hitherto implicit grounds, which together constitute a greater challenge to contemporary religious philosophy than has been realized. Religious philosophers need to find a better way around PCC than has been found, or, if PCC is unavoidable, religious philosophers need to work toward a worldview that both accepts PCC and defends strong forms of religious experience.