Passion and transgression
Wharton shows the difficulties of repressed and illicit passion, passion without any sanctioned outlet. Ethan has had a loveless marriage, and Mattie Silver has been the catalyst for some very powerful emotions. Passion is blocked by social convention and circumstance. Wharton is a devotee of naturalism, and in many of her novels the environment is the true shaper of men's destinies. Ethan's situation dooms his passion for Mattie Silver. But passion should not necessarily be seen as a potential liberator; in the novel passion seems more like yet another force that robs men of their agency.
Determinism/Naturalism
Determinism is an important theme in this novel and in many of Wharton's other books. Starting with late-nineteenth century American literature, exposure to Darwin and thinkers like Huxley and Spencer began to have a strong influence on American novelists. Naturalism, the school of thought that makes individuals subject to forces of heredity and environment, was a new philosophical force in novels and plays. Individuals have little or no agency, and the environment destroys or nurtures as it sees fit. A person is either born to adapt or made to fail. In Ethan Frome, the influence of this Darwin-inspired outlook is undeniable. Wharton links it to an older form of determinism, the harsh philosophy of New England's old Calvinists, by choosing Starkfield, Massachusetts as her setting. The historical backdrop of Puritanism is for atmosphere rather than for religious instruction: there is little God in Wharton. The environment, which can be natural, cultural, or situational, is the force that decides men's fates.
The land and the people
The connection between the land and the people is a recurring theme of the novel. The narrator is amazed by the harshness of the Starkfield winters, and through his experience of the winter he comes to understand the character of the people. In her introduction to the novel, Wharton talks of the "outcropping granite" of New England, the powerful severity of its land and people. This connection between land and people is very much a part of naturalism; the environment is a powerful shaper of man's fate, and the novel represents this relationship by constantly describing the power and cruelty of Starkfield's winter.
Isolation
Rural New England in winter is a land under siege, with tiny towns and tinier farms separated by vast expanses of cold and snow. The isolation is both physical and emotional. Ethan feels from a young age that he is alone in his sensitivity to natural beauty and his curiosity about science. By the time of the narrator, the tragedy of Ethan Frome has removed him even farther from the other people of Starkfield. The narrator remarks that in a town like Starkfield, people's lives are harsh enough so that they have little time to alleviate the pain and troubles of others.
Lost potential
This theme is closely connected to the themes of determinism, connection between the land and the people, and isolation. As Starkfield is not a nurturing world, Ethan's curiosity and intellect have had few outlets. Both in his youth and in his old age, the disparity between his intellectual curiosity and the limitations of his environment is painful. By the time the narrator meets him, Ethan is not only the ruin of the man that he was, but the ruin of the man that he could have been.
Loss and transience
Wharton also creates a feeling of loss and transience. Wharton uses the flashback structure to draw attention to buildings that once were beautiful that now have decayed. In Frome's youth the buildings are new and handsome, whereas by the time the narrator sees them they are old and faded. Beginning with Chapter 1, the tone of the descriptions is much more sensual: there is a sense of the town as a living place, with smells and colors described evocatively. But we are looking at the past, and it is a far cry from the dead world the narrator of the opening shows us. The effect is a very bleak portrayal of the relationship between a small town and the passage of time. In a big city, old buildings become historic, or they are replaced by new buildings. In Starkfield, old buildings simply fall into disrepair. Family fortunes dwindle, and men like Ethan Frome fade and deteriorate as slowly and certainly as the buildings of their immediate environment. The most horrible contrast is between the young and vibrant Mattie Silver and the broken and hateful old crone that the narrator meets in Chapter 10.
Poverty
From the author's own introduction to the novel, written in 1922 and included in most editions, there is a sense of frustration with earlier portrayals of rural life in New England. Wharton is reacting against a kind of literature that romanticizes poverty and rural life. She depicts rural life as incredibly harsh. Poverty's greatest curse is that it takes away options. It traps Ethan at the farm, just as later it forces Ethan, Zeena, and Mattie to live under the same roof.