William Blake’s poem “The Book of Thel”, like many of his other works, is concerned with innocence and experience. The poem’s motto alludes to the biblical book of Ephesians and specifically to the twelfth chapter, which presents the idea that all life will eventually die. The second half of the four-line motto asks, “Can Wisdom be put in a silver rod? Or Love in a golden bowl?” While these lines echo Ephesians 12:6, the rod and bowl may also serve as sexual symbols in the poem.

"The daughters of Mne Seraphim led round their sunny flocks. All but the youngest; she in paleness sought the secret air." These first lines of "The Book of Thel" set the scene for the entire work by showing one girl slipping away from her sisters. The young girl, whose name is Thel, seeks solitude.

She walks to the river and begins to question many of the natural objects that she encounters. “Why fades the lotus of the water? Why fade these children of the spring? born but to smile & fall.” Thel wonders why the beautiful flower dies and then immediately thinks of her own mortality. “Thel is like a watry bow,” she says, “and like a parting cloud. Like a reflection in a glass. like shadows in the water.” In these lines Thel alludes to ephemeral objects: a rainbow, a cloud, a reflection, and a shadow, and she realizes that her life will be just as brief as these.

Lines 16-18 present an Edenic scene, as Thel thinks of her own death: “Ah! Gentle may I lay me down, and gentle rest my head, And gentle sleep the sleep of death and gentle hear the voice of him that walketh in the garden in the evening time.”

Thel then encounters a lily of the valley, a flower that is reborn every year. Thel realizes, however, that her own death will be permanent. In line 41, Thel says that at her death “I vanish from my pearly throne, and who shall find my place?” Her death will result in a complete loss of her identity.

In part II of the poem, Thel questions a cloud about mortality. The cloud is able to accept its short life without complaint, making Thel feel alone and isolated. “I pass away: yet I complain, and no one hears my voice,” she explains. In fact, Thel has lost the ability to appreciate the simple joys of nature because she is so concerned about her own death. She wonders if her only purpose is “to be at death the food of worms.” In this line, Thel recognizes the life cycle, but she protests her part in it.

Eventually Thel is given the opportunity to enter “the land unknown” and return unharmed. There, she sees the dead and soon approaches her own grave. She hears a voice that asks, “Why cannot the Ear be closed to its own destruction?” This may be her own voice speaking from the grave. Thel would prefer to shut out this knowledge. She chooses to turn away from the truth that her own life will end, and “with a shriek,” she flees back to the valley where she lives.