The preacher’s problem is that relevance is decided not only by what the hearer can and will hear, but what he needs to hear whether or not he wants to, and the latter may not be communicable in language he will naturally understand. The language can be bent only so far, till it is bent out of shape. The apostles of relevance do not see this problem, and hence toss away the truths they genuinely want to convey.This is something that I need to watch out for.
Because the right word is often the unusual or technical or “outdated” word, the preacher should not abandon a specifically Christian vocabulary even though the man in the pew may not understand it right away, and even though he may find it off-putting or even offensive. These words will be the language of the insider, and therefore almost by definition irrelevant to the outsider the preacher wishes to bring inside and many of those who are already inside but lack the conscious and energetic commitment of the real insider. Link