From the historical account of the trajectory of Christianity, Léon Denis presents the origin of the Gospels, the communion of the first Christians with the Spirits and the spirit phenomena present in the Bible,reinforcing the principle that the Spiritist and Christian guidelines are,in fact,perfectly linked as a single doctrine. A well-known follower of Allan Kardec, the author explains how mediumistic practice and reincarnation were erased from Christian thought, and how the rituals and dogmas that were established - often going against the simplicity of Christ – were based on the relationship with Roman Catholicism.