Wilde uses anthropomorphism throughout the story to create a fairy-tale landscape in which animals and elements of the natural world speak and act like humans—something that invites readers to suspend their disbelief and revisit their assumptions about the differences between humans and nature.
At the very beginning of the story, the Nightingale hears the Student and is moved by his sorrow, saying “here at last is a true lover.” This detail immediately implies that the reader should suspend disbelief and take for granted that the animals in this story are capable of feeling and speaking. In other words, giving animals human qualities gives the story a sense of whimsy and fantasy that forces readers to use their imagination.
The plants in "The Nightingale and the Rose" are also given human qualities. Not only can the trees speak, but they're also given human-like anatomy. When answering the Nightingale’s request for a rose, for example, the trees are described as shaking their “heads,” and when receiving the Nightingale’s sacrifice, the third tree says how the Nightingale’s “life-blood must flow into my veins”. By assigning a human anatomy to the trees, the story portrays the trees as living and breathing creatures, which forges a connection between humans and nature as a whole.
This connection also ironically demonstrates the human characters' coldness. The Student’s oblivious response to the Nightingale’s sacrifice contrasts with the Oak-tree, whose request for one last song and admittance that he “shall feel very lonely” when the Nightingale is gone demonstrates a sentimentality that is absent in the human characters. Indeed, humans in the story prove entirely oblivious to nature's liveliness and inherent value. The Student cannot understand the Nightingale when she speaks or sings to him, and the Professor’s daughter cannot understand the value of the rose. By setting up this contrast (in which nature is sentient while humans are oblivious and unfeeling), Wilde subverts expectations, forcing readers to engage more critically with the story. This choice also arguably comments on the unfeeling rationalism and cold industrialism of the modern age.
There's a sense of irony at play in "The Nightingale and the Rose" that subverts the expectations of the fairy tale genre, thus providing a social commentary on the rationalist age in which Wilde lived.
The Student's devotion to intellectualism and rationality ultimately proves ironic, since he turns out to be one of the most foolish and irrational characters in the text. Wilde highlights this through the use of dramatic irony. When the Nightingale tells the Student about the sacrifice she is going to make in order to secure him his desired red rose, the Student is unable to understand her. Responding to her song, he says:
"She has form, [...] that cannot be denied to her; but has she got feeling? I am afraid not. In fact, she is like most artists; she is all style, without any sincerity. She would not sacrifice herself for others. She thinks merely of music, and everybody knows that the arts are selfish."
Wilde uses dramatic irony in this moment, as it has already been made clear that the Nightingale is the most selfless character in this story. And yet, the Student suggests that she's "selfish." Immediately after this speech, the Nightingale flies to the tree and sacrifices herself for the Student's love. The claim that "she would not sacrifice herself for others" thus spotlights the Student's ignorance.
Once the Nightingale has sacrificed herself to create the red rose, the Student looks out his window and says:
"Why, what a wonderful piece of luck!" he cried; "here is a red rose! I have never seen any rose like it in all my life. It is so beautiful that I am sure it has a long Latin name"; and he leaned down and plucked it.
The contrast between the vivid passage that precedes this (in which the Nightingale presses her breast against the thorn and gives her blood to stain the rose) and the Student's exclamation of "luck" is intentionally stark, again highlighting his ignorance. That the Student praises the rose's beauty by saying it must "have a long Latin name" emphasizes the irony of his supposedly educated worldview, which he uses to translate beauty into legible knowledge.
What's more, the irony of the entire situation becomes even more apparent when the Student later dismisses love as a "silly thing" with no practical use, returning to his "great dusty book"—the dustiness of which suggests that, for all his pretentious beliefs that intellectual pursuits are inherently worthwhile and practical, the books to which he has devoted his time are actually obscure and removed from the workings of everyday life. The irony, then, is that he criticizes love as an impractical thing, only to then devote himself to something that is even more useless and arbitrary than human emotion.