Louise Gluck has long practised poetry as a species of clairvoyance. She began as Cassandra, at a distance, in league with the immortals. To read her books sequentially is to chart the oracle’s metamorphoses into unwilling vessel, reckless, mortal, down-to-earth. “The Seven Ages” is Gluck’s ninth book, one of her strangest and certainly her most bold. In it – like William Blake’s mystical Thel – she gazes down at her own death and in so doing forces endless superimpositions of the possible on the impossible. Her act at once defies and embraces the inevitable and is finally mimetic. Over and over, at each wild leap and transformation, flames shoot up the reader’s spine. In an essay she writes, “one of the revelations of art is the discovery of a tone or perspective at once wholly unexpected and wholly true to a set of materials”. This truth to materials -language, occasion, antecedent – is the proof of a poem.