In his almost forty-year career as a theologian, Hendrik M Vroom has become an intelligent observer and authority in the field of religious diversity. For more than a century Western theology has been exposed to rigorous criticism, while granting space to other worldview traditions. What was once common has lost its self-evidence, leading to intriguing questions. Do theistic religions worship the same God? Do religions have "the same" morality? Do they accept "the same" rules for accounting what one believes? And as our world becomes more pluralistic as religions change and affect each other, how can their followers be certain about their beliefs and moralities? These are stimulating and essential questions for anyone interested in the phenomenon of religion.