Archibald MacLeish famously wrote:

   "A poem should not mean
    But be."

I can think of no poet who so consistently fulfils MacLeish’s dictum as Marianne Moore.

Randall Jarrell talks of “her lack – her wonderful lack – of arbitrary intensity or violence, of sweep and overwhelmingness and size, of cant, of sociological significance”. Her poems simply exist; they “cannot be suborned to any end but their own”¹. They are elegant and precise; carefully constructed and meticulously detailed; and always, always, wonderfully rewarding.

— Thomas

Biography

Born near St. Louis, Missouri, on November 15, 1887, Marianne Moore was raised in the home of her grandfather, a Presbyterian pastor. After her grandfather’s death, in 1894, Moore and her family stayed with other relatives, and in 1896 they moved to Carlisle, Pennsylvania. She attended Bryn Mawr College and received her B.A. in 1909. Following graduation, Moore studied typing at Carlisle Commercial College, and from 1911 to 1915 she was employed as a school teacher at the Carlisle Indian School. In 1918, Moore and her mother moved to New York City, and in 1921, she became an assistant at the New York Public Library. She began to meet other poets, such as William Carlos Williams and Wallace Stevens, and to contribute to the Dial, a prestigious literary magazine. She served as acting editor of the Dial from 1925 to 1929. Along with the work of such other members of the Imagist movement as Ezra Pound, Williams, and H. D., Moore’s poems were published in the Egoist, an English magazine, beginning in 1915. In 1921, H.D. published Moore’s first book, Poems, without her knowledge.

Moore was widely recognized for her work; among her many honors were the Bollingen prize, the National Book Award, and the Pulitzer Prize. She wrote with the freedom characteristic of the other modernist poets, often incorporating quotes from other sources into the text, yet her use of language was always extraordinarily condensed and precise, capable of suggesting a variety of ideas and associations within a single, compact image. In his 1925 essay “Marianne Moore,” William Carlos Williams wrote about Moore’s signature mode, the vastness of the particular: “So that in looking at some apparently small object, one feels the swirl of great events.” She was particularly fond of animals, and much of her imagery is drawn from the natural world. She was also a great fan of professional baseball and an admirer of Muhammed Ali, for whom she wrote the liner notes to his record, I Am the Greatest! Deeply attached to her mother, she lived with her until Mrs. Moore’s death in 1947. Marianne Moore died in New York City in 1972.

– www.poets.org

Moreover

Here’s an extract from a review (by Frank Kermode) of Moore’s “Selected Letters”, in which he talks about her poetic method:

“Moore once remarked that ‘prose is a step beyond poetry … and then there is another poetry that is a step beyond that’: you had to go through prose to come out the other side purged of that disposable prior poetry, with its irrelevant inversions and its subjection to conventional rhythms. The posterior poetry would have built into it the virtues of good prose. In the syllabic poems, where ‘each stanza’ is ‘a duplicate of every other stanza’ (much as Donne set himself argumentative problems by exactly replicating an arbitrarily complicated opening stanza), the sentences could, indeed must, be capable of being written straight out as prose; what is lost in the process of doing that is precisely the machine-like precision of the repetitions of line length and covert rhyme. If the effect seems mechanical, so be it. In 1932, on the brink of celebrity, she remarked that ‘a thing so mechanically perfect as a battleship is always a pleasure to me.’

One can see something of what this means by looking at ‘The Steeple-Jack’, the poem which, though not an early work, having been published in 1932, stands first in both the Collected Poems of 1981 and the Selected Poems of
1941. It was much admired by both Eliot, who arranged the order of the poems for Moore, putting this one at the head, and by Wallace Stevens, who analysed it at some length, commending, among other things, the poet’s attachment to truth. The opening six-line stanza sets the arbitrary pattern of line length and rhyme, and has a full close:

 Dürer would have seen a reason for living
   in a town like this, with eight stranded whales
 to look at, with the sweet sea air coming into your house
 on a fine day, from water etched
   with waves as formal as the scales
 on a fish

(Dürer because he travelled far and fruitlessly to inspect a beached whale, but also because of the etched scales; and, more generally, because he is deeply in the thought of the poem.) The second and third stanzas repeat the stanza pattern but form a continuous sentence which flows over the scheme without disturbing it, stopping at the last line of the third stanza. The fourth stanza strictly observes the pattern and the rhymes, one of which, ‘the’ and ‘sea-‘, is virtually not there.”

– http://www.lrb.co.uk/v20n08/kerm2008.htm