The man and the girl act as foils for each other in this story, meaning that their juxtaposition reveals important qualities of the other's character. While it’s clear that both characters enjoy traveling and living a life of leisure—their bags contain labels “from all the hotels where they had spent nights”—by the time the story starts, they are on very different pages about their future. Though they never reference the girl’s pregnancy directly, they spend the entirety of the story arguing about whether or not she should have an abortion.
Despite Hemingway’s sparse use of language, it quickly becomes clear that the girl wants to give up their life of extravagance and travel in order to raise this baby and build a family. The man, on the other hand, suggests that having this baby would ruin their relationship, taking away their option to live lives of freedom and exploration.
Through this argument, Hemingway is highlighting an age-old dynamic that often arises in romantic relationships: family vs. freedom. The fact that the man and the girl are not given names (apart from the man using a pet name to refer to the girl as “Jig”) suggests that Hemingway is intentionally juxtaposing the dynamic between a stereotypical man and a stereotypical woman, using them as foils to expose certain societal patterns. In the story, the man ultimately seems to get his way, perhaps highlighting the unequal power dynamic between men and women in society generally.