I find Chesterton a somewhat mixed bag , and that applies to his poetry also, but this has always moved me deeply, and is all the more effective for concealing its theme until the last stanza:
When fishes flew and forests walked
And figs grew upon thorn
Some moment when the moon was blood
Then surely I was born.
With monstrous head and sickening cry
And ears like errant wings
The devil’s walking parody
On all four-footed things.
The tattered outlaw of the earth,
Of ancient crooked will;
Starve, scourge, deride me: I am dumb,
I keep my secret still.
Fools! For I also had my hour;
One far fierce hour and sweet:
There was a shout about my ears,
And palms before my feet.