This book offers the keys to understand the various conceptual assumptions that serve as a consistent and possible foundation of religious thoughts.

The development of the history of humanity is also a history of the development of religions. They have deployed, parallel to the ritual praxis, thought structures that base reflections in themselves different and, at the same time, coherent. However, the diversity of religions constitutes a challenge for "those who have a different belief", especially when they appear as reform, improvement or correction of previous religions.

Why they believe what they believe presents to each of the great religions - Judaism, Christianity, Islam, Hinduism and Buddhism - from their internal structure to make them understandable in their relationship. In this way, the work unfolds what could be the essential themes of interreligious dialogue offering this, in turn, a splendid contribution both for those who reflect on the religious phenomenon and for those who profess a belief.