"The Book of Thel" is a poem by William Blake, published in 1789. It tells the story of a young girl named Thel who questions her existence and the nature of life and death. Thel is portrayed as innocent and curious, seeking answers from various elements of nature, including a lily, a cloud, and a worm. Throughout her journey, Thel grapples with themes of mortality and the transient nature of life. Ultimately, she learns that life is a cycle of creation and destruction, leading her to a deeper understanding of her place in the world. The poem reflects Blake's broader philosophical and spiritual ideas.