Poetry, I told myself this morning, is stained glass. Language is like a sheet of glass, a window. Beautiful, often; functional, it allows us to see the world without being in it, and usually we catch our own reflection as we look, fading ghostlike into the landscape. Hard and unyielding, language can be melted and reformed, though it always comes back to what it is, what it was.

Poetry takes a hammer to language, sometimes brutally, sometimes with the care of a sculptor chipping marble from the hidden image, always with an engraver’s eye. The poet looks at these glittering fragments and picks those most interesting to them, though they may cut their fingers as they handle the shards. They reassemble them into something beautiful, something new, something different and often something difficult. They may paint the fragments, creating opaque patches we struggle to peer through, and bind them together with the lead of rhyme and meter. They present them to the world not as windows to look through but portals through which the light from outside falls.

The greatest poems – sad, angry, sensual, whatever mood they provoke, however they push at us – illuminate our internal world, create an atmosphere of reverence not in the dusty, polish-fogged space of a stone church but in the open cathedrals of our minds.