This poem was written when the dominant fear for mankind was the threat of nuclear war: that threat may have receded a little, in our consciousness if not necessarily in reality, but only to be replaced by the realisation that when it comes to inflicting irreparable harm on our natural environment, attrition in the end works just as well as Armageddon. It’s a fine poem, but the problem I have with it now is a feeling that this may be one occasion where Wilbur’s restraint, his cool elegance of diction, work against him: that the time for the courtly elegiac is past and what we need now are words of fire and rage.
Advice to a Prophet
When you come, as you soon must, to the streets of our city,
Mad-eyed from stating the obvious,
Not proclaiming our fall but begging us
In God’s name to have self-pity,
Spare us all word of the weapons, their force and range,
The long numbers that rocket the mind;
Our slow, unreckoning hearts will be left behind,
Unable to fear what is too strange.
Nor shall you scare us with talk of the death of the race.
How should we dream of this place without us?
The sun mere fire, the leaves untroubled about us,
A stone look on the stone’s face?
Speak of the world’s own change. Though we cannot conceive
Of an undreamt thing, we know to our cost
How the dreamt cloud crumbles, the vines are blackened by frost,
How the view alters. We could believe,
If you told us so, that the white-tailed deer will slip
Into perfect shade, grown perfectly shy,
The lark avoid the reaches of our eye,
The jack-pine lose its knuckled grip
On the cold ledge, and every torrent burn
As Xanthus once, its gliding trout
Stunned in a twinkling. What should we be without
The dolphin’s arc, the dove’s return,
These things in which we have seen ourselves and spoken?
Ask us, prophet, how we shall call
Our natures forth when that live tongue is all
Dispelled, that glass obscured or broken
In which we have said the rose of our love and the clean
Horse of our courage, in which beheld
The singing locust of the soul unshelled,
And all we mean or wish to mean.
Ask us, ask us whether with the worldless rose
Our hearts shall fail us; come demanding
Whether there shall be lofty or long standing
When the bronze annals of the oak-tree close.
Richard Wilbur
David Sutton 
I love this, David. For an update, one can easily substitute “Spare us all word of the gases, their parts per million.” As for fire and rage, most people are weary of it. Here in the U.S., lawns display signs boosting the candidacy of “Giant Meteor 2020.” We are beginning to “dream of this place without us.”
Regarding “Xanthus” in verse 6: In The Iliad Book 21 Xanthus calls to the river Simois to help him drown Achilles, but Hera intervenes, calling her son Hephaestus to battle the river with his fire. Under his blaze, the river boils until Xanthus promises to submit.
The poem was first published in 1959. “locust” (in the penultimate verse) – grasshoppers (which include locusts) hatch from an egg into a nymph or “hopper” which undergoes five moults, becoming more similar to the adult insect at each developmental stage.
The “live tongue” in verse 7 is when human beings draw on nature to express “all we mean or wish to mean”. “how we shall call / Our natures forth when …” – eg how shall we aspire to hearts of oak when there are no more oaks?