There are four ways in which a preacher or guild speaker can treat any Christian doctrine: (a) proclaim it; (b) explain it; (c) defend it; (d) prove it. This last way is clearly ruled out where the doctrine of the Trinity or indeed any mystery of faith is concerned, though the temptation to try and prove anything and everything is one to which I suspect the C.E.G. mind, so commonly pre-occupied with apologetics, is peculiarly prone. I think it is very important for the C.E.G. speaker to remind himself constantly that there is a world of difference between an apologetic argument in defence or support of the faith and a proof. An apologetic argument, when addressed at least to the unbeliever, can never be more than persuasive, attractive, suggestive. There can never be any mathematical certainty about it, or an overwhelming weight of evidence, and that is what the word proof normally means to most of us.