Here’s a wise caution for all preachers, teachers, and writers who frequently draw from the vocabulary of the faith — words like sin, grace, Christ, and a host of other sanctified terms that emerge over time within our particular circles — but who are tempted to use the terms without ever stopping to explain their meaning. Helmut Thielicke explains the danger, and then proposes one helpful practice, in his book The Trouble with the Church: A Call for Renewal (Harper & Row, 1965), pages 36–38:

Where is the average person today who, when he hears the word “sin,” really hears what the New Testament meant by that word? For whom today does this word still say that here man is being addressed at the point of his resistance and opposition to God, that this means man in his will to assert his autonomy, his insistence that everything centers in man, his incredible passion for security, his lostness in preoccupation with the moment and that which is tangible and immediately at hand? And yet all this must be heard when we hear the word “sin,” if for no other reason than to understand that it is possible for a sinner to be at the same time an example of moral perfection and that he need by no means be a criminal, an antisocial, or even a person who lacks seriousness. Were not the Pharisees ethically very respectable people? And yet for Jesus they were more drastic examples of sin than publicans and prostitutes.

And the word “Christ” itself? What would really be the result if we were to investigate the exchange value of that term in the psychological substructure of the average man today? What we would come out with would probably be some idea of a fabulously wise man or a perfect human being.

The point is that we need to say what we mean by these terms; we dare not throw them at people as supposedly valid coins whose value is immediately recognized. Otherwise we shall all too thoughtlessly reach out for them with the notion that they are perfectly familiar, whereas the truth is that the metal begins to glow and burn only when we have some idea of what these coins really signify. …

I once experimented with students, having them prepare sermons in which the conventional terms like “God,” “sin,” “grace,” etc. did not appear. The words had to be paraphrased. I think this is a good exercise, even though it has importance only as an interim practice. For we should not discontinue the use of these words in the pulpit; all we need is a withdrawal-cure because of the thoughtless use we make of them. We need to learn to overcome the temptation to string together the old words in different variations, because then souls remain underfed and are lost.