"La Belle Dame sans Merci" delves into the universal theme of unrequited love through the eyes of a desolate narrator grappling with rejection. While stories and songs often celebrate mutual love, unrequited love emerges when one person's feelings far outweigh those of the object of their affection. The root "requite" means "to repay," implying an anticipated balance in romantic relationships and highlighting the perceived injustice when love is given but not reciprocated.

In the poem, the knight’s sense of betrayal would be less severe if he hadn’t initially believed that the fairy child shared his level of affection. She appears to fall for the knight just as he falls for her. Her gaze in line 19 and her "sweet moan" in line 20 could be seen as signs of her affection, while the gifts she offers suggest mutual feelings. She even invites him to her home, her "elfin grot," making him feel comfortable. Naturally, he assumes she is equally interested in continuing their budding romance when he awakens.

It's uncertain whether the knight's deep sadness upon discovering her absence is primarily because he lost her or because he realizes she never loved him as much as he thought. By the poem's conclusion, he clearly feels deserted but shows no anger toward her. The only clues about whether the lady ever loved the knight are from the ghostly figures in his dream, who describe her as merciless and pitiless. These dream images might be interpreted psychologically, indicating that the knight subconsciously knew she had left him, and his mind was already starting to blame her. The dream could be his way of rationalizing, portraying her as cruel to cope with the pain of unreciprocated love.

The poem's romantic tale is intricately intertwined with imagery from nature. The woman whom the knight loves is portrayed as a fairy's child, connecting her to rural folklore traditions. She is described with "wild" eyes and as living in a cave on a hillside. During their time together, the knight and the lady exchange gifts crafted from flowers, roots, honey, and dew. When the knight awakens to find the lady missing, the world around him is depicted as lifeless, with imagery reflecting nature's winter demise: squirrels have stored their food for the barren months, the lake's grass has withered, and the birds have ceased to sing. The only hints of life left are the fading ones on the knight's face. The "lily" on his brow, observed by another speaker in the poem, symbolizes a once-delicate beauty now linked to death. The rose color in his cheek shows he was touched by beauty, yet it is also "fading," much like the rest of nature.

Despair is the feeling of having lost all hope, believing that life will never be good again. In "La Belle Dame sans Merci," the knight experiences despair when a promising relationship suddenly ends. From the poem's opening line, it's clear that something is seriously wrong, as a stranger discovers the knight in the forest and immediately perceives his distress. The knight's pallor and his decision to linger by a dead, frozen lake prompt the stranger to ask about his condition, specifically what has caused his emotional turmoil.

In the middle stanzas of the poem, the knight narrates a romance that was more significant to him than anything before or since. This brief relationship concluded with the lady lulling him to sleep. Readers can infer that, feeling content and joyful with her, the knight anticipated that their love would continue to flourish when he awoke.

In reality, unlike in a magical world, a knight's despair would take time to develop, as he wouldn't immediately know if his beloved was truly gone forever. However, in the enchanted world of this poem, the knight is visited in his dreams by pale apparitions of noblemen who describe the woman as heartless. Upon waking and finding her gone, he quickly accepts that her absence confirms the harsh words spoken by the apparitions. The poem does not show the knight searching for her or trying to understand why she left; he is as certain of her intention to leave as he is of his love for her. There is no hope for their reunion, and consequently, no hope that he will ever find happiness again. His life is sentenced to despair.

The enigmatic allure of the femme fatale has intrigued literary critics and readers alike, and nowhere is this more evident than in the enduring fascination with "La Belle Dame sans Merci." This poem has sparked a wealth of critical discourse, with Bate noting the myriad sources that contributed to its creation. Among these influences is the eerie folk ballad "Thomas Rhymer," which weaves its own tale of enchantment and danger.

The character of the beautiful lady in "La Belle Dame sans Merci" clearly embodies the archetype of the femme fatale. This figure, emerging from ancient myths and persisting through the ages, epitomizes the seductive yet treacherous qualities that captivate and ensnare the unwary. The femme fatale archetype is mirrored in the evolution of the vamp in modern popular culture, illustrating its timeless appeal.

Bate identifies Edmund Spenser’s Duessa from The Faerie Queene (1590, 1596) as a significant influence on Keats's portrayal. In Spenser's epic, Duessa seduces the Red Cross Knight, a narrative of seduction and downfall that resonates with the themes in "La Belle Dame sans Merci." Furthermore, Keats likely drew upon historical narratives of powerful men, such as Samson and Antony, who were similarly undone by the charms of beguiling women.

The tale of the knight, ensnared by a mysterious and enchanting woman, echoes the timeless narrative of mortals caught in the thrall of otherworldly beings. This theme, steeped in myth and literature, reminds us of Odysseus's companions in Homer’s Odyssey, whom Circe transforms into swine, stripping them of their humanity. Similarly, the knight in Keats’s narrative suffers a fate that is harrowing in its subtlety; robbed not only of his vitality, as suggested by his “death-pale” complexion, but also of his agency and purpose.

The imagery of the knight’s desolation is stark. Once a figure defining chivalric action and valor, he is now confined to a barren land where “no birds sing.” This place, devoid of life and movement, mirrors his spiritual and physical depletion. The knight, reduced from noble endeavors to idle wandering by the lake, embodies the tragic irony of a formidable warrior rendered impotent. This transformation evokes the passive languor of Tennyson’s lotus eaters and Mariana, who are equally detached from the vibrancy of human existence.

Yet, the knight's plight is not solely self-inflicted. He is a victim of forces beyond his understanding or control, ensnared by the enchanting presence of the femme fatale. This supernatural encounter drains him of his will, rendering him a passive recipient of his own ruin. The tragedy lies in his resignation to this fate, his surrender to the inexorable pull of despair and loss. In relinquishing his struggle, he embodies the profound sense of fatalism that underscores the narrative. The knight, thus, becomes an emblem of irrevocable loss, his story a somber reflection on the human condition's vulnerabilities when faced with the seductive pull of the unknown.

The enigmatic figure of the lady in "La Belle Dame sans Merci" has sparked varied interpretations among critics, each offering a unique perspective on her elusive nature. While some view her as a dangerous menace, there are others who challenge this perception and delve deeper into the nuances of her character.

One such critic, Bate, posits that the poem underscores the "ultimate impossibility of contact between the human and this elusive, only half-human figure." Bate questions the inherent sinister nature of the lady, pointing out that the knight's encounter with the "horrid warning" of potential starvation occurs only in a dream. This dream, Bate suggests, might echo the knight's own internal fears and anxieties rather than a direct threat posed by the lady herself.

Similarly, Earl R. Wasserman, in his work The Finer Tone (1953), offers another perspective by absolving the lady of any evil intent. Wasserman views her as an ideal—the quintessential object of desire that the lover must pursue, yet can never truly possess. He argues that the knight is destined to endure her "unkindness," a trait that stems from her nature rather than from any malicious intent. In this interpretation, the lady becomes a symbol of unattainable beauty and desire, highlighting a tragic, inevitable gap between longing and fulfillment.

The depth and breadth of critical analysis surrounding Keats’s "La Belle Dame sans Merci" underscore the intricate layers of meaning hidden beneath its deceptively simple language. Critics have long debated the poem’s true interpretation, grappling with its rich tapestry of themes and symbolisms. Despite the varied perspectives and interpretations, one certainty remains: the poem has etched itself into the literary canon as a masterpiece. Its haunting beauty and enigmatic narrative continue to captivate scholars and readers alike, ensuring its enduring legacy in the realm of great poetry.