I am to talk about apologetics. Apologetics means of course defense. The first question is –What do you propose to defend? Christianity, of course: and Christianity as understood by the church in Wales. And here at the outset I must deal with an unpleasant business. It seems to the layman that in the Church of England we often hear from our priests doctrine which is not Anglican Christianity. It may depart from Anglican Christianity in either of two ways: (1) It may be so “broad” or “liberal” or “modern” that it in fact excludes any real supernaturalism and thus ceases to be Christian at all. (2) It may, on the other hand, be Roman. It is not, of course, for me to define to you what Anglican Christianity is–I am your pupil, not your teacher. But I insist that wherever you draw the lines, bounding lines must exist, beyond which your doctrine will cease to be Anglican or to be Christian: and I suggest also that the lines come a great deal sooner than many modern priest think. I think it is your duty to fix the lines clearly in your own minds: and if you wish to go beyond them you must change your profession.
This is your duty not specifically as Christians or as priests but as honest men. There is a danger here of the clergy developing a special professional conscience which obscures the very plain moral issue. Men who have passed beyond these boundary lines in either direction are apt to protest that they have come by their unorthodox opinions honestly. In defense of these opinions they are prepared to suffer obloquy and to forfeit professional advancement. They thus come to feel like martyrs. But this simply misses the point which so gravely scandalizes the layman. We never doubted that the unorthodox opinions were honestly held: what we complain of is your continuing you ministry after you have come to hold them. We always knew that a man who makes his living as a paid agent of the Conservative party may honestly change his views and honestly become a Communist. What we deny is that he can honestly continue to be a Conservative agent and to receive money from one party while he supports the policy of another.
Even when we have thus ruled out teaching which is in direct contradiction to our profession, we must define our task still further. We are to defend Christianity itself–the faith preached by the Apostles, attested by the Martyrs, embodied in the Creeds, expounded by the Fathers.
–C.S. Lewis, God in the Dock, ed. Walter Hooper (Grand Rapids: Eerdmans, 1970), pp.89-90 (emphasis mine)