Few social historians had examined the popular religious beliefs of the 1500s at the time Thomas published Religion and the Decline of Magic in 1971. His analysis of how deeply held beliefs in witchcraft, spirits, and magic evolved during the Reformation remains one of the great works of post-war scholarship. Thomas concludes that belief in magic once served a purpose, helping people understand and cope with everyday problems. But scientific progress and religious change led to more rational thought and a drive to disengage magic from religion, diminishing magic's power. His analysis allowed him to claim that social history can answer important questions about changes in fundamental beliefs.