Much of O. Henry’s writing, "The Last Leaf" included, was written within a literary tradition called Naturalism, a modified form of Realism and a precursor to Modernism, which would come to dominate the literary scene in the United States very soon after (beginning around 1914). Naturalism, which began in France in the middle of the 19th century, focused on depicting everyday life realistically and without imposing any kind of moral judgment. The movement broke from Realism in its interest in scientific determinism, which is the idea that the human character is shaped most fundamentally by its environment (including social and economic conditions), as well as other forces out of its control (e.g. heredity).
Naturalism’s deep interest in the effects of socio-economic environment on the human psyche is reflected in some aspects of the pneumonia outbreak in the story. O. Henry chooses to focus on the effect of the pneumonia outbreak on those living in the most difficult environment within the city, e.g. the impoverished. The theme of community as a means of survival within the piece also plays into the discussion of how environment can shape human destiny. Scenes of rough living—poverty, the criminal underbelly of cities—were often the subjects of works in this genre, and O. Henry’s depictions of a gritty Greenwich Village fit easily into this mold as well.
However, there are some elements of The Last Leaf which are incongruous with a totally Naturalistic approach to literature. The sentimental tone of the story, thanks in part to the strong thematic role of friendship, cuts against the basic pessimism reflected in many works within Naturalism. In addition, O.Henry’s work is known for its emphasis on morality, and The Last Leaf’s glorification of self-sacrifice in the name of friendship feels more Romantic than Naturalistic. What’s more, the role of Johnsy’s emotional journal in directing her physical health seems more in line with Romanticism’s prioritization of emotion over reason. All of these elements in O. Henry’s work reflect a Romantic sensibility in tension with his Naturalistic style.
