How can setting influence or shape the theme of a story or poem?
Setting, which is time and place, is a powerful means of creating or influencing a theme in literature. Let's look at one short story, one novel, and one poem to see how setting contributes to each.
First, in "The Lottery," we are shown a charming village on a beautiful summer day, but not in a specific time or place, really "Anywhere, USA." This is meant to lull us into believing it is going to be a pleasant story that could happen in any village. The charm of the village as we begin creates a sharp contrast to the evil of the village at the end of the story. This bucolic beginning sets the stage for our shock later on and also creates a kind of universality to the theme, which is that the nicest of people anywhere can commit the most dreadful of acts, all in the name of a quaint "tradition." If the story were more firmly bound to a particular time and place, or if it began with too much of a hint of evil, it would lose a great deal of its effectiveness.
Next, in The Great Gatsby, the setting is New York and Long Island in the Roaring Twenties. Gatsby, Nick, and the Buchanans live in wealth in Long Island, while George and Myrtle Wilson live next to the Valley of Ashes, symbolic of their poor, grey lives. The backdrop of the novel is Prohibition, the rise of organized crime, and the great partying, drinking, carelessness, and amorality of the wealthy. All of this reflects and reinforces the themes of the novel, which is about money, morality, or the lack thereof, and the American Dream. The twenties were a time of great inequality, far more, I would guess, than even today, since capitalism was much less regulated and the federal income tax had been instated only a few years prior. It is difficult to imagine this novel in any other time and place, with its setting so perfectly in sync with its themes.
The poem "The Listeners" is set deep in the countryside, and there is kind of "hush" to this poem it could never have had the narrator walked up to a door to an apartment in Manhattan. There is nothing quite as dark and quiet as the country at night, and the entire mood of the poem, mysterious and haunting, telling of some tragedy that has happened because someone was too late, is dependent on its setting for its effect.
I'm fairly certain there must be some story or poem in which setting is not important, but as I sit here, I cannot think of a one! Authors have good reasons for the settings they choose, and as you read stories and poems, you will be able to see what a difference the settings make. Try to imagine a story happening in some other time and place, and that will help you to see how important the setting really is.