I did Pause for Thought on BBC's Radio 2 Chris Evans Show this morning.

I wanted to think about the importance of imagination – for good or ill. Having been in Eisenach, I wanted to contrast the imagination of Johann Sebastian Bach and Martin Luther with the horrors of Hitler's boys – birthed in the same place. But, the tone wasn't right for the particular medium of the Breakfast Show. S, I re-wrote it on the train to London yesterday evening. And this is how it ended up this morning:

Don't ask me why – cos I can't stand the thing – but I can't get John Lennon's Imagine out of my head. I have to forgive him a bit, though, because when Liverpool were rubbish at the beginning of last season, the line “Above us only sky” etched into his statue at John Lennon Airport was added to with the words “and below us only Wolves and West Ham”.

But, the reason I can't get the song out of my head has to do not with Lennon or his fantasies, but rather with the importance of imagination in shaping our lives and our society. Maybe it has something to do with the fact that I've just got back from Germany where I was preaching in the church in Eisenach where Johann Sebastian Bach was baptised and where Martin Luther preached.

Now we're talking! Johann Sebastian was one of many Bachs, but his vision of God, the world and what human life is all about fired his creative imagination to write some of the most sublime music in history – he saw behind the mundane and the music soared.

Luther, too, rebelled against powers and authorities that turned people's eyes down into the muck of human failure instead of up into the sheer generous freedom of forgiveness and a new start. What's more, he did a bit of a Bach and wrote loads of songs to celebrate it all.

Of course, the place of Bach and Luther was later the place where unspeakable things took place – as happens when our imagination goes bad. Yet, with Bach and Luther, the Old Testament prophets provoke our imagination to see beyond the present reality and be held by a vision of a better, more just and merciful future. Jesus does the same by teasing our curiosity with images of a different way of being and loving and living.

I want to keep my imagination fired up. Like Bach and Luther. And even John Lennon.