Julien Ries gave birth to fundamental religious anthropology, the gaze that allows us to go to the heart of every religion and culture and discover the homo religiosus that animates it. Dialogue implies reciprocity with other religions and cultures and pluralism must not be considered a deviation from Christianity but a richness. The relationship between Christians and other religions has been complex, starting with their marginalization in the Roman Empire and their retaliation against the pagans when Christianity became the religion of the empire. In the Middle Ages, the rediscovery of Greek philosophy will not soften the disagreement with polytheism and other disagreements will develop both with the Jews and with Islam and dualisms. The path of dialogue will be long, made even more difficult by European colonialism. Important precursors are to be found in various periods: from humanistic figures such as Nicola Cusano to shepherds such as Newman in the nineteenth century. With the Second Vatican Council, what the precursors hoped for became reality. The declaration "Nostra Aetate" becomes the basis for dialogue between religions and cultures and an important part of Christians - and among them great theologians, thinkers and witnesses - become propagators of a dialogic culture that finds support from the Popes.