This was explained over the course of centuries through a complex theological form of processing. The centuries from the foundation up to the VII century were afflicted by the disputes on the twofold human and divine nature of Jesus and on the Trinity. The issues were defined by the Councils of Nicea and Constantinople (IV century) that established the Creed, and by that of Chalcedon (V century). The problems relating to the nature of the Church and the supremacy of the bishop of Rome, of the freedom of worshippers in the interpretation of the Holy Scripture, of the nature of the sacraments, the relationship between divine grace and human freedom, between faith and works, were at the centre of the schisms and the theological conflicts that lead to the great schism of the East and to the protestant Reform that determined the dissolution of the unity of Christianity and its fragmentation into a plurality of Churches and confessions, each of them firm in their defence of their own experienced based dogmatic truths as exclusive and set against the others. It is above all in the XX century, with the establishment of ecumenism and the deep resumption of interest in the catholic field exercised by the Second Vatican Council, that new relationships between Christians and Christians with other religions were asserted .