We do not put our trust in techniques. Nevertheless, Martin Luther did not despise the teaching of certain principles of communication that he thought were important. There are things preachers can learn regarding how to construct and deliver a sermon, and how to communicate information effectively from the pulpit.
He also said that the makeup of the human person is an important clue to preaching. God has made us in His image and has given us minds. Therefore, a sermon is addressed to the mind, but it's not just a communication of information—there is also admonition and exhortation (as noted above). There is a sense in which we are addressing people's wills and are calling them to change. We call them to act according to their understanding. In other words, we want to get to the heart, but we know that the way to the heart is through the mind. So first of all, the people must be able to understand what we're talking about. That is why Luther said it is one thing to teach in seminary, as he did at the university, and another to teach from the pulpit. He said that on Sunday mornings, he would pitch his sermons to the children in the congregation to make sure that everyone there could understand. The sermon is not to be an exercise in abstract thinking.
That which makes the deepest and most lasting impression on people is the concrete illustration. For Luther, the three most important principles of public communication were illustrate, illustrate, and illustrate. He encouraged preachers to use concrete images and narratives. He advised that, when preaching on abstract doctrine, the pastor find a narrative in Scripture that communicates that truth so as to communicate the abstract through the concrete.
In fact, that was how Jesus preached. Somebody came to Him and wanted to debate what it meant to love one's neighbor as much as oneself. "But he, wanting to justify himself, said to Jesus, 'Who is my neighbor?' Then Jesus answered and said: 'A certain man went down from Jerusalem to Jericho, and fell among thieves…'" (Luke 10:29–30). He didn't just give an abstract, theoretical answer to the question; he told the parable of the Good Samaritan. He answered the question in concrete form by giving a real-life situation that was sure to get the point across.
Jonathan Edwards preached his famous sermon "Sinners in the Hands of an Angry God" in Enfield, Conn. He read the sermon from a manuscript in a monotone voice. However, he employed concrete and even graphic images. For instance, Edwards said, "God… holds you over the pit of hell, much as one holds a spider, or some loathsome insect, over the fire." Later he said, "The bow of God's wrath is bent, and the arrow made ready on the string." He also declared, "You hang by a slender thread, with the flames of divine wrath flashing about it." Edwards understood that the more graphic the image, the more people were likely to hear it and to remember it.
Luther said the same thing. He was not substituting technique for substance, but saying that the substance of the Word of God must be communicated in simple, graphic, straightforward, illustrative ways to the people of God. That was the whole of the matter for Luther—the minister is to be a bearer of the Word of God—nothing less, nothing more. In this way the preacher teaches the people of God.
This excerpt is taken from R.C. Sproul's contribution in Feed My Sheep.