Topical preaching is very popular these days, partly on the theory that unchurched people can be attracted by what appear to be self-help messages: "Successful Financial Management," "The Problem Of Suffering," "Raising Well Adjusted Children," etc.
It is theoretically possible to preach an expository message on a topic - if you are preaching a passage of Scripture that deals with a topic - but this is not what most modern topical messages are like. Rather, the topical messages I hear today are built on the preacher's outline of what he wants to say. The Scriptures are usually brought in to support the preacher's points, but they are not usually dealt with in any depth. They are used as "proof texts" and are often presented without any context that would show that they apply to the topic at hand.
I want to be an expository preacher. Most of my sermon series are book studies. I prepare by studying the text to be preached as thoroughly as I can manage. I look for a way to organize the message around the points that are made in the text and in a way that is true to the text.
But I am always nervous. Am I really getting the point of the passage? Am I reading into the passage what I think it should say? Am I guilty of using proof texts when I bring in other passages for support? At the end of the message have I really explained the text at hand or simply promoted my own point of view?
These are serious questions. They need to be asked. They cannot be ignored. But they shouldn't paralyze us - we do our best with the gifts God has given us. And we cannot let them drive us away from expository preaching and into simple topical lectures.
Whatever people may think they need, what they really need is the word of God.
(2Tim 3:16-4:2) ¶ All Scripture is given by inspiration of God, and is profitable for doctrine, for reproof, for correction, for instruction in righteousness,
17 that the man of God may be complete, thoroughly equipped for every good work.
1 I charge you therefore before God and the Lord Jesus Christ, who will judge the living and the dead at His appearing and His kingdom:
2 Preach the word! Be ready in season and out of season. Convince, rebuke, exhort, with all longsuffering and teaching.