'...be very careful to think about your audience's premises. Don't assume, for example, that everyone listening trusts the Bible. So when you make a point from the Bible, it will help to show that some other trusted authority (such as empirical science) agrees with the Bible. Use it to promote trust in the Bible, saying something like, "See, the Bible was telling us centuries ago what science now confirms." That will help convince your hearers of that point so you can move on. By the end of the sermon, of course, you will be appealing only to God's Word, but in the early stages of the sermon you invite non-believers along by showing respect for their doubts about the Bible's reliability.'
Timothy Keller, Center Church, p.177.
