While theories about interpreting biblical and other parables have long realised the importance of readers’ responses to the topic, recent results in social psychology concerning systematic self-deception raise unforeseen problems. In this paper I first set out some of the problems these results pose for the authority of fictional thought-experiments in moral philosophy. I then consider the suggestion that biblical parables face the same problems and as a result cannot work as devices for moral or religious instruction in the way (...) that they are usually understood to work. I examine a number of influential theories about interpretation of the parables which might appear to deflect the problems, and argue that none of them are ultimately successful in doing so. (shrink)