Holy See
Although the Holy See is sometimes metonymically referred to as the "Vatican", the Vatican City State was distinctively established with the Lateran Treaty (1929) between the Holy See and Italy to ensure the temporal, diplomatic, and spiritual independence of the Papacy. As such, ambassadors are officially accredited to the Holy See and not the Vatican City State. Conversely, Papal nuncios to states and international organisations are recognised as representing the Holy See and the integrity of the Catholic Church along with its 1.3 billion members, not the Vatican City State, as prescribed also in the Canon law of the Catholic Church (1983). The "Holy See" thus refers to the See of Rome viewed as the central government of the Catholic Church. The Catholic Church, in turn, is the largest non-government provider of education and health care in the world, while the diplomatic status of the Holy See facilitates the access of its vast international network of charities.
World Council of Churches
Pope St. John XXIII took a different stance however, and in 1958 he was elected as the head of the Catholic Church. Ecumenism was a new element of catholic ideology which had been permitted, which was signified to a great extent, when John XXIII met with the then Archbishop of Canterbury, Geoffrey Fisher. This was the first meeting between an Archbishop of Canterbury, and the Pope in the Vatican for 600 years. John XXIII later developed the office of the Secretariat for Promoting Christian Unity; which symbolised a dramatic shift in support for the ecumenical movement, from the Catholic Church, led from the Vatican. 1961 saw Catholic members attend the Delhi conference of the WCC, which masked a significant shift in attitude toward the WCC from the Papacy. There was the idea in addition to this, that the Pope invited non-Catholics to attend the Vatican II council. This new approach to inter-denominational relations was marked within the Unitatis Redintegratino.