The advantage of a fixed form of service is that we know what is coming. Ex tempore public prayer has this difficulty: we don’t know whether we can mentally join in it until we’ve heard it — it might be phoney or heretical. We are therefore called upon to carry on a critical and a devotional activity at the same moment: two things hardly compatible.
[The rigid form] also prevents getting too completely eaten up by whatever happens to be the preoccupation of the moment (i.e. War, an election, or what not). The permanent shape of Christianity shows through. I don’t see how the ex tempore method can help becoming provincial and I think it has a great tendency to direct attention to the minister rather than to God.
— C.S. Lewis
Bologna 