This is the script fo this morning's Pause for Thought on BBC Radio 2's Chris Evans Show in the company of Mo Farah, Tamsin Greig, Robert Winston and Jamie Lawson:

I have a theory about children's books. It's not original: children's books are mainly read by adults. By adults, for adults. Remember when Harry Potter was just starting out on literary life and the publisher had to use two covers: one for kids and a different one for grown-ups … just so the latter wouldn't get embarrassed on a train?

I think part of the reason for this might be that loads of adults are learning that imagination is not just for the little ones, and words open up new worlds of wonder.

I remember being accused of using simple language in one of my books. Accused, I think, because the reviewer thought I should posh up a bit and be more academic. But, the genius of good communication is to make the complex simple, not the simple complex.

I am no stranger to this. Every time I open the gospels I am confronted by stories and images. This stuff isn't meant to hit you with some solid truth, but to get your imagination working – sneaking round the back of your mind when you're not expecting it, and scratching away at your memory. “Where God is,” says Jesus, “is like a mustard seed.”

What?! What's that supposed to mean? Use your imagination! Something tiny grows in unlikely places into a whacking big tree in whose branches the birds make their nests – and the tree doesn't get to choose which birds. Get it? God is to be found where there is hiddenness, outrageous growth, unlikely generosity, hospitality. You get the idea?

A couple of days ago I was in a primary school at Low Moor in Bradford. I was giving certificates to young leaders who, together, had made a difference to their local community in a variety of ways. They had learned to look for what others didn't see – like litter and the absence of birds – and did a rubbish collection and built bird boxes. They learned to be surprised by the difference they could make. Leading meant taking responsibility instead of waiting for others to do it for them. Brilliant.

And they were full of imagination at a world they are still discovering.

So, keep the books coming. Keep the stories rolling. Keep the imagination fired up – and try growing up into a child.