What is the central idea or theme of 'Lucy Gray' by William Wordsworth?

The central theme of "Lucy Gray" by William Wordsworth revolves around the innocence and purity of nature as embodied by the character of Lucy. The poem explores themes of solitude, loss, and the connection between humanity and the natural world. Through Lucy's tragic fate, Wordsworth reflects on the enduring presence of love and memory, suggesting that even in death, the beauty of nature and the spirit of the individual remain intertwined. Ultimately, it highlights the fragility of life and the profound impact of nature on the human experience.