Seeing Seamus Heaney is a bit like seeing someone who should be dead, in that it’s only by the grace of God you’re alive at the same time as him. The stroke he had in 2006 nearly killed him, and now his hands flutter gently when he holds a book. I would say he’s less substantial than he was but the tremble gives him a slightly ethereal quality: not fragile, but somehow less earthbound. I…