Although "Paul's Case" did not receive much critical attention when it was first published in 1905, it has become Cather's most frequently reprinted and read short story. A Public Broadcasting Corporation (PBS) television adaptation in 1980 revived critical interest in the story.

According to Loretta Wasserman, in ''Is Cather's Paul a Case?,'' one reason the story has historically garnered little notice is because the character of Paul is so unlike Cather's other characters. Whereas most of her fiction takes place in the plains and prairies of the Midwest, "Paul's Case" takes place in smoggy Pittsburgh and glamorous New York. Critics have taken pains to see the story as a fitting end to the short story collection in which it first appeared, The Troll Garden. All of the stories in this book concern artists or people of artistic or sensitive temperament who cannot resist the dangerous lure of the gardens of art. James Woodress, in his introduction to The Troll Garden, claims that Paul consumes the ''forbidden fruit'' of art, leading to his tragic end. Susan Rosowski, in The Voyage Perilous: Willa Cather's Romanticism, argues that Paul loses himself to the temptations of romantic fantasy.

Unlike other characters in The Troll Garden, however, Paul is not an artist at all. Many critics believe he does not even have an artistic temperament. Instead, they argue that Cather is writing a psychiatric "case study." Wasserman argues that Paul is emotionally maladjusted, living in a fantasy world and lacking a firm grip on reality. In her study Willa Cather's Short Fiction, Marilyn Arnold argues that Paul is "half-crazy" and cannot describe either reality or art reliably. John A. Weigel, in a CEA Critic article, describes how he applied a psychological test to Paul's character and concludes that he is a schizophrenic.

Others ascribe Paul's behavior to social, rather than psychological, causes. David A. Carpenter, in an essay in American Literature, sees Paul as a victim of his environment. "The uncreative, superficial and life-destroying values perpetuated in the homes of Pittsburgh" produce in Paul an unhealthy desire for wealth and luxury. In Carpenter's view, the portraits of John Calvin and George Washington that hang above Paul's bed suggest that these are American values. Paul achieves the ends of success without the means, however, and so remains responsible for his actions. He "has consumed himself morally and ethically by living a lie—one purchased through someone else's hard work," according to Carpenter.

Critics ascribing genetic or social causes for Paul's behavior agree that he is "destroyed by his own illusions," as Wasserman puts it. Sharon O'Brien, in Willa Cather: The Emerging Voice, considers whether Paul's "probable homosexuality" corresponds to a similar inclination of Cather's. When Cather adopted masculine dress and the name "William Cather, Jr." as an adolescent, she, like Paul who dresses as a dandy, was rejecting the restricting conventions of her day. But Cather's ironic attitude toward Paul signals her belief that there is a difference between loving art and the beautiful places it is found and creating it oneself. Cather both identifies with and distances herself from Paul's selfish, escapist tendencies. Larry Rubin, writing in Modern Fiction Studies, and Claude Summers, in Studies in Short Fiction consider the possibility of Paul's homosexuality as well. They point to his physical appearance, temperament, and the brief description of his night out in New York with the boy from Yale. But, these critics argue, Paul's thin grasp on reality and his aestheticism, which alienates him from most people, make it impossible for him to recognize and integrate his homosexuality into his life.