This is the most scientific book of Allan Kardec. It deals with themes regarded as incontestable by religion, in the light of the immortality of the soul, unifying Christian thought and scientific discoveries. It offers us a unique opportunity to know and study themes of universal interest, discussed in a logical, rational and revealing way. It analyses, with coherence, the origin of the planet Earth, and avoids mysterious or magical interpretations about the creation of the world. It also analyses the question of miracles, explaining the true nature of the supernatural facts of the Gospels. Finally, it talks about a new generation, whose rising will be the landmark of a new Era for Humanity, based on the practice of justice, peace and friendship.