Jerome Gellman has recently disputed my claim that a naturalistic explanation for mystical experiences is available, a better explanation than any current attempt to show that God is sometimes perceived in those experiences. Gellman argues (i) that some mystics do not ‘fit’ the sociological explanation of I. M. Lewis; (ii) that the sociological analysis of tribal mysticism cannot properly be extended to theistic experiences; and (iii) that mystical experiences merit prima facie credence, so the burden of proof falls on the naturalist. I reply (i) that the alleged counter-examples either do fit Lewis's explanation or are too poorly known to judge; (ii) that Lewis's theory, supplemented by recent neurophysiological findings, provides a strong explanation for all mystical experiences; and (iii) that the burden of proof, if there is one, now falls on the theist.