But what is the Church? Where is the Church? Bewildered and disoriented, many Christians do not find sure answers to these questions. And they come to believe that perhaps the answers which the Magisterium has formulated for centuries — and which good catechisms have proposed with the necessary precision and simplicity — have now been superseded and must be replaced by new ones. A series of facts and difficulties seem to have come together to darken the bright countenance of the Church. Some maintain that the valid Church can be found only in their personal zeal to accommodate it to what they call modern times. Others cry out: the Church is nothing more than man's desire for solidarity. We ought to change it, they say, in accord with present circumstances.

They are wrong. The Church today is the same one Christ founded. It cannot be any other. The Apostles and their successors are the vicars of God with regard to the rule of the Church as instituted through faith and with regard to the sacraments of the faith Hence, just as it is not lawful for them to constitute any other Church, so too it is not lawful for them either to hand down any other faith or to institute any other sacraments. Rather, the Church is said to have been built up with the 'sacraments which flowed from the side of Christ hanging on the Cross'. The Church must be recognised by the four marks in the profession of faith of one of the first Councils, as we pray in the Creed of the Mass: One, holy, catholic and apostolic Church.

These are the essential properties of the Church, which are derived from its nature as Christ intended it. And, being essential, they are also marks, signs, which distinguish it from any other human gathering, even though in the others the name of Christ may be pronounced.

A little more than a century ago, Pope Pius IX briefly summed up this traditional teaching: The true Church of Christ is constituted and recognised, by divine authority, in the four marks which in the creed we affirm as to be believed. And each of these marks is so united with the others that it cannot be separated from them. For this reason, that which truly is catholic and is called Catholic should at the same time shine forth by the prerogatives of unity, of holiness and of apostolic succession. It is, I emphasise, the traditional teaching of the Church, which the Second Vatican Council has repeated again, even though in recent years some may have forgotten it, led by a false ecumenism. This is the sole Church of Christ which in the Creed we profess to be one, holy, catholic and apostolic, which our Saviour, after his resurrection, entrusted to Peter's pastoral care, commissioning him and the other apostles to extend and rule it, and which he raised up for all ages as the pillar and mainstay of the truth.