Final answer:
The assertion regarding twentieth-century drama's adherence to a single genre like neoclassicism is false. Modernism, which dominated the era, was noted for its innovative and genre-blending techniques introduced by influential playwrights like Eugene O'Neill, Arthur Miller, and Tennessee Williams, clearly diverging from the neoclassical purity of genre.
Step-by-step explanation:
The statement that drama in the early mid-twentieth century tended towards a purity of genre similar to neoclassicism, with no mixing of realism, anti-realism, or expressionism, is false. Early and mid-twentieth-century drama, particularly during the Modernism movement, was characterized by a radical shift from traditional narrative forms and classical principles of dramaturgy. The era saw the emergence of various American playwrights like Eugene O'Neill, Arthur Miller, and Tennessee Williams who significantly shaped Modern Theatre.
In Modernism, traditional boundaries were often blurred, merging different styles to create new forms of storytelling on stage, bringing forth realism and anti-realism, alongside other methods like expressionism. Modernist playwrights aimed to reflect the immediate, changing realities of their time, often employing innovative techniques to comment on society, politics, and human psychology. This period was anything but 'pure' in terms of sticking to one genre or another; it actively defied the neoclassical ideals of purity of genre.