Shelley builds his argument on an unusual comparison. He doesn't start with the villain. He starts with a hunt. In the first stanza a lama, "most fleet of the sons of the wind," is no match for the lion or the tiger. It sinks "in a trance of despair" and bleeds out on the sand while the Indian rocks echo its death-cry, "protracting the horrible harmony." That last phrase is chilling because it makes agony sound like music. The scene is vivid, but it is really a set-up for the real subject, which is human intolerance.
The second stanza turns on a surprising claim. Even the great bird of prey, "thirsting--ay, thirsting for blood," kills only for food, and is therefore "more lenient, more gentle" than mankind. Its violence has no theatre around it: "Revenge does not howl in the dead," and "ambition" does not crown "the murderer's head." Nature's predators are cruel, but they are honest about it. Human cruelty, the poem implies, adds motives like glory, grudge and ambition, and so is worse.
The third and fourth stanzas bring in the speaker and the real enemy, the "Bigot," who is "fiercer than tiger." The speaker sets out to "draw from the purest of fountains." Judging by the imagery, this fountain stands for truth or free thought, whose "waves" are "too pure, too celestial, for mortals to see." The Bigot is never described as a body, unlike the lion and tiger. We see only his effects: a shadow that "eclipses the day," "darkness of deepest dismay," "corpses, that rot on the ground." He is less a man than a climate of fear, and that vagueness makes him harder to escape. The light-and-dark contrast sharpens the point. Those who drank from the fountain "bathed for awhile in its silvery beam," while the Bigot's influence blots out the sun.
The sound of the poem supports this story of pursuit. Each stanza has nine lines rhymed roughly ABABBCCDD, and the pattern never changes, which gives the poem a trapped, relentless feel. The rhythm is mostly galloping anapaests ("Dares the lama, most fleet of the sons of the wind"), which suggest running feet. Then the lines shrink, so that "The monster transfixes his prey" and "On the sand flows his life-blood away" arrive short and final, like a pounce. Each stanza ends on a pair of rhymes that hits like a closing door. The echoing phrase "fast-fleeting footsteps of air" returns in stanza three, and the verb "flee" and "fly" carry the chase from the animals to the speaker: "'Tis in vain that I fly."
The most telling movement is emotional. In stanza three the speaker is defiant, "Yet, yet will I draw," and the doubled "yet" sounds like someone talking himself into courage. By stanza four the speaker has taken the lama's place as prey, and the damage is personal: "The most tenderly loved of my soul / Are slaves to his hated control." The Bigot's real power lies not in killing the speaker but in capturing the people he loves. The poem ends on a question with no answer except surrender: "What remains, but to curse him,--to curse him and die?" The repeated "to curse him" and the dash show a voice running out of strength, and it is the opposite of the confident defiance earlier.
Whether the poem is moving or overheated is for the reader to judge. Its emotion is loud, its animals rather exotic (a "lama" among "India's rocks," for instance), and its despair complete. But it stands as a clear early statement of an idea that Shelley, a major English Romantic poet, is known for: that tyranny over belief is a worse violence than the violence of nature. By making the tiger look almost innocent, the poem forces us to ask what is more savage, an animal that kills to eat or a person who destroys minds in the name of certainty.