This section is dense and tangled, far from the suspenseful action sequences that McEwan does better than any of his literary contemporaries. Yet it repays close attention, for McEwan has gifted Tom with his own articulacy, that lucid, encompassing prose. The theme here, as McEwan explains on his website, is not so much the unknowable future as our present, the present as it might look to those yet to come. “As they look back at us, what will our descendants think, when they contemplate the diminished world we left them?”