:It's the theory that there is no heaven or hell, and that descriptions of such within religious texts are actually describing the individuals own mental/spiritual state as a result of their own guilt or lack therefo, rather than the judgement of some deity.  However, the sentence is very POV, in that it labels this theory the "moderate" one, thus taking sides in the anti-religion debate by labeling all judgeing-god religious beliefs "extremist" by inference.  Tom S.