It is often said that Catholics believe in the development of doctrine. But it is not a doctrine of the Catholic Church that doctrine develops. The teaching of the Church is that its faith is immutable. The Church’s primary attitude to doctrine is the principle given by St Paul. ‘Even if we, or an angel from heaven, should preach to you a gospel contrary to that which we preach to you, let him be accursed. As we have said before, so now I say again, if anyone is preaching to you a gospel contrary to that which you received, let him be accursed’ (Galatians 1:8). There is, of course, an obvious sense in which doctrine does develop. For the number of defined doctrines has grown over time. But the Catholic view of this is that doctrines defined over time are contained in or implied by what was taught from the beginning. The primary role of the Church as teacher is to preserve what has already been given and to state what that amounts to as need arises. It retains the Gospel and articulates it.

If that is what the Church does, it seems fair to ask why we should believe what the Church teaches. Some would dispute this on the ground that the Church in a sense does not teach. ‘Why should we believe it?’ presupposes that someone has propounded what he takes to be a truth.