Archibald MacLeish, who like Cummings arrived on the poetic scene after the first imagists had created the new movement, nevertheless can be credited with the poetic summing up of imagism in his "Ars Poetica" in 1926, written well after the imagist decade had ended. It is inconceivable that such a poem could have been written without imagism, because the technique as well as the philosophy of MacLeish's most famous poem is imagist. It consists of a sequence of images that are discrete but that at the same time express and exemplify the imagist principles and practice of poetry.

The Latin title is borrowed from Horace, who wrote a prose treatise in the first century A.D., the Silver Age of Rome, called "Art of Poetry," advising poets among other things to be brief and to make their poems lasting. MacLeish wanted to link the classical with the modern in his poetic "treatise" as a way of implying that the standards of good poetry are timeless, that they do not change in essence though actual poems change from age to age and language to language. His succession of opening images are all about the enduring of poetry through time, as concrete as "globed fruit" or ancient coins or stone ledges, and as inspiring to see as a flight of birds or the moon rising in the sky. The statements are not only concrete but paradoxical, for it is impossible that poems should be "mute" or "Dumb" or "Silent" or "wordless," which would mean that there was no communication in them at all; rather, what MacLeish is stating in his succession of paradoxical images is that the substance of poetry may be physical but the meaning of poetry is metaphysical: poems are not about the world of sensible objects as much as they are about invisible realities, and so the universal emotions of grief and love can be expressed in words that convey the experience in all its concreteness, yet the words reach into the visionary realm beyond experience, toward which all true images point. The final paradox, that "A poem should not mean but be," is pure impossibility, but the poet insists it is nevertheless valid, because beyond the meaning of any poem is the being that it points to, which is ageless and permanent, a divine essence or spiritual reality behind all appearances. MacLeish's modern "Art of Poetry" is a fulfillment of the three rules of imagism (be direct, be brief, and use free verse), of Pound's definition of the image, and at the same time of Horace's Latin statement on poetry, that good poetry is one proof that there is a permanence in human experience that does not change but endures through time.