Preaching in an authoritarian manner is preaching in a cultivated style that is intended to convey the thought that this person has authority. The preacher is wearing it on his sleeve, so to speak. He is making a big deal of the fact that he has authority, and he's pushing it down your throat. That's what the word authoritarian means. It's a confidence trick because none of us have authority like that. The authority that we have as preachers is the authority that Calvin had: The authority of those who faithfully echo and apply what's there in the Bible text. Just that.
You could parallel it to the centurion in the Gospel story (Matthew 8:5–13). We have authority because we're under authority. The authority is God's authority, but we share it when we're under it, and the sharing is a matter of relaying what we realize is true for us. Think of the man in the story. He says: I'm a man under authority. Because I am under authority, I can exercise authority. Ultimately it's the authority that I am under which I exercise. I say to one, come, and he comes, I say to another go, and he goes, and so on and so forth.
Avoid preachers who are playing the confidence trick of an authoritarian manner. It makes people believe that they have authority, when they really don't. A preacher should make it plain that the authority remains in God, in God's Word, and that he or she only has authority to tell others what they need to do because he or she is under that authority themselves. It's a point to keep banging away at, I think. Our culture needs it. There are so many preachers who don't grasp it. It spoils their preaching.
J.I. Packer is an executive editor of CT and a professor of theology at Regent College in Vancouver.