'A. E. Houseman memorably said: I could no more define poetry than a terrier can define a rat. It’s not an easy matter to justify one’s decisions when faced with numerous poems from which to make a limited selection. There’s no programmatic guide to what makes a poem successful although the impact of a good poem is something we all know and recognise. Generally it has something to do with registering a sense of shock – it might be the shock of the new, unexpected or strange, or it might be the shock of the familiar – it can take one off guard to be confronted by what one knows but didn’t know one knew. And what creates the shock? This is different with every poem. It may be linguistic – the relationship between the words or the acoustics of words and lines; it may be the imagery or information or impressions communicated; it may be the tensions and dynamics set up between all or some of these elements that results in a poetic imperative. The ineffable subtleties at work in a poem are endlessly unpredictable; it’s that unpredictability that makes poetry so compelling. You never know in what way a poem is going to reach you.' (Introduction)