In “Naïve Modernism,” I argue that the simplicity, freedom, and imaginative world-making often associated with childhood are central to the work of William Carlos Williams, Gertrude Stein, and Lorine Niedecker. Each of these poets has more than once been dismissed as childish—simplistic, nonsensical, or slight—and each has also been redeemed in the name of sophisticated or more “adult” aesthetic and intellectual seriousness. Here I take these writers seriously while also attending to the ways in which their writing is truly childlike or childish. Indeed, “Naïve Modernism” proposes that these writers need not adhere to the codes of grown-ups to be taken seriously. ,In characterizing these writers as “naïve,” I take up Friedrich Schiller’s well-known account of artless, simple immediacy in On Naïve and Sentimental Poetry. Schiller is helpful in describing the childlikeness of Williams, Stein, and Niedecker, but their work also in turn expands and complicates Schiller by adding the elliptical, erratic, and crafty possibilities of child-mind to his picture of noble innocence. Furthermore, this modernist naïveté is not entirely artless or natural. Williams, Stein, and Niedecker each in their own ways seek immediacy, but they are all also careful, knowing artificers. In their poems we see how the naïve mode can itself be a culturally mediated performance of childlike or “folk” qualities—a sentimental sort of naïveté. To articulate a new concept of the naïve that accommodates these modernist versions of childlikeness, I supplement Schiller especially with Walter Benjamin’s and D.W. Winnicott’s ideas about childhood and play. ,The dissertation also locates Williams, Stein, and Niedecker in an international network of modernists that includes such figures as Eliot, Pound, H.D., Stevens, Breton, and Duchamp. Within the seriousness and authority of sophisticated “high” modernism, “Naïve Modernism” seeks out provisional zones of playful non-compliance. My aims are not only to understand three particular poets more fully and to reveal new literary-historical aspects of modernism, but also to learn from modernist poems some new ways of imagining our own adulthood.