Wordless as the flight of birds

I came across this poem, ‘Ars Poetica’ by Archibald Macleish, while doing some work on poetics and poetic theory. I think it beautifully captures what a poem is or should be, without tedious explanations or what the Greeks called periergia. Macleish (1892-1982) was among other things America's Librarian of Congress. 

A poem should be palpable and mute
As a globed fruit,

Dumb
As old medallions to the thumb,

Silent as the sleeve-worn stone
Of casement ledges where the moss has grown--

A poem should be wordless
As the flight of birds.

*

A poem should be motionless in time
As the moon climbs,

Leaving, as the moon releases
Twig by twig the night-entangled trees,

Leaving, as the moon behind the winter leaves,
Memory by memory the mind--

A poem should be motionless in time
As the moon climbs.

*

A poem should be equal to:
Not true.

For all the history of grief
An empty doorway and a maple leaf.

For love
The leaning grasses and two lights above the sea--

A poem should not mean
But be.