It is very difficult to produce arguments on the popular level for the existence of God. And many of the most popular arguments seem to me invalid. Some of these may be produced in discussion by friendly members of the audience. This raises the whole problem of the ‘embarrassing supporter’. It is brutal (and dangerous) to repel him; it is often dishonest to agree with what he says. I usually try to avoid saying anything about the validity of his argument in itself and reply, ‘Yes. That may do for you and me. But I’m afraid if we take that line our friend here on my left might say etc. etc.’
C.S. Lewis, "Christian Apologetics" (1945) included in God in the Dock (Eerdmans, 1970) 100.