Ideological movements, be they religious or secular, are demanding and Procrustean movements. By ideological movements I mean those that demand of their adherents resolute belief in some “deep set of truths” posited by a deity, by supposed immutable historical laws, or by some other equally unchallengeable source. Their followers, once initiated, or even just born into the fold, are expected to stay there and, as the saying goes, “keep the faith.”
However, in cultural, political and religious terms there are no eternal deep truths. History has an abrasive quality that erodes our beliefs in this god and that law. Though the process might take a longer or shorter time to manifest itself, yesterday’s faith will at some point start to ring less true. At some point followers start to fall away.