"All sermons are good," said the saintly 19th-century clergyman John Keble to a student who praised one that he had heard.

Well, yes.

And then again, no.

One of the problems with being an occasional preacher oneself is that if you start pontificating about it, people think you are claiming to be able to do it particularly well. Nothing – really, nothing – could be further from the case. When I hear a sermon nowadays I'm more likely to think "I wish I'd said that" than "I wish he hadn't".

But here's the thing: I passionately believe in preaching, and I'm not sure how widely that view is shared. I come from a classical Nonconformist position – I take some pride in having been described as a "hairy Baptist" – in which the sermon, rather than the Eucharist or the prayers, is at the heart of the service. That, I suspect, is rare and getting rarer. In many evangelical churches today the heart of the service is what's described, in a way that is theologically nonsensical, as the "worship" – that is, lots of songs. Having done that, the congregation settles down to the "teaching" – that is, the sermon.

That's where it galls me, because equating preaching and teaching is a fundamental mistake. The English word "preach" is from a Latin word meaning "proclaim", which translates the Greek word kerusso in the Gospels. Arguing from a dictionary is a pretty sterile business, but at least it highlights an element in preaching today without which it's less than it should be: that it should proclaim, announce, commend, two life-changing, world-shaking truths, namely that the Kingdom of God has come and that Jesus is Lord. We don't primarily listen to sermons to be taught stuff, whether it's biblical history, doctrine or Greek. A sermon is a different sort of animal.

This is why I worry when I see that the preacher has come prepared with a PowerPoint presentation. It's the wrong model: they don't want us to look at them, to share what God has given to them and connect with them through their eyes and their voice: they want us to look at a screen, and follow a lecture.

That's why I worry about preachers who rely too much on their notes. I do it myself – but if I feel I need to go off-piste, I'll take the risk.

That's why I worry when preachers are fixated on the Bible, with every statement cross-referenced and every sub-clause analysed. I blame Martyn Lloyd-Jones, who was a devil for that (with respect). I grew up under one of his disciples, admittedly a really fine preacher, who took two years to go through Ephesians. I don't think any of us knew any more about Ephesians when he'd finished than when he started. Here's a thought: most Christians through most of history have either not had Bibles or, if they had them, would not have known how to read them. The Word became flesh – so how come, in so many churches today, we turn him back into words?

Preaching comes from the heart and soul, not just from the mind. Preaching, as Martyn Lloyd-Jones said – he had many good points – is "logic on fire". Preaching is taking words that are two or three thousand years old, distilling them in the magical retort that is the human mind and tossing in a lighted match. It's imagination, passion, conviction. When the preacher stands in the pulpit or at the lectern, the congregation needs to hear not just his or her words, but God rocking their world.

Do we learn stuff at the same time? Of course. The preacher will have grappled with the text beforehand, maybe for hours. The commentaries will have been read, the ramifications of different interpretations teased out, the precise sub-species of the lion killed by Benaiah the son of Jehoiada in a pit on a snowy day established (1 Chronicles 11:22; there is one in Bristol Zoo). Some of this might even find its way into the finished sermon. But that isn't the point of the exercise, any more than building a ski-jump is the point of a different exercise. The point is the opening of the heart and mind to a different reality. A sermon should be dangerous, a whoosh into the unknown with no guarantee of a safe landing.

There are lots of criticisms of preaching. People don't have the same attention-span that they used to, thanks to the internet and everything. Our culture is visual nowadays, not aural, and people aren't used to being talked at. Some people learn kinesthetically, or inter-personally, or intra-personally, or spatially. But actually, all these criticisms are aimed at teaching, not preaching – that is, the conveying of information, interpretations or opinions from one person's brain into another's. Every single one of them is probably valid, and it's when the preacher tries to do this in a 20-minute lecture that so-called "preaching" fails. Our Bible teaching is probably better in small groups, with a variety of learning styles. But if we lose the confidence to believe that heart can speak to heart, that a called and anointed preacher can proclaim God's truth in a way that strikes to the roots of our being, we've lost something very precious.

Mark Woods is a freelance writer and Baptist minister.