The title of The Prelude was selected posthumously, not chosen by William Wordsworth himself. While he was working on the poem, he referred to it in letters as merely "Poem (title not yet fixed upon) to Coleridge," and in fact the work was intended to function as a precursor to a collaborative work called The Recluse, which was never completed. This dedication to fellow Romantic poet and collaborator Samuel Taylor Coleridge wasn't merely a behind-the-scenes fact of the work's creation. Instead, Wordsworth addresses Coleridge regularly throughout the text, building out his friend as a character within the poem itself. The version of Coleridge he creates is drawn in broad strokes. Readers get the impression of a man with a deprived childhood, or at least a childhood deprived of nature. Whereas Wordsworth portrays himself as having had the artistic and psychological benefits of an idyllic, enriching childhood—despite being orphaned at a young age—he portrays Coleridge as having overcome disadvantage with great effort. This version of Coleridge learns to love nature, to care for humankind, and, of course, to develop poetic genius above all odds. Later in The Prelude, the friends are separated when Coleridge leaves for Italy to improve his health. Wordsworth, back in England, is hopeful for his friend's improvement and remains endlessly grateful to him.
The Prelude, however, is a poetic work, and while it can provide a great deal of insight into Wordsworth's life, it doesn't tell the full story of these two poets' tumultuous friendship. The friendship began in 1797, when Coleridge—who had previously had only a short meeting with Wordsworth—arrived at the Dorset home of Wordsworth and his sister Dorothy. His arrival prompted a period of intense collaboration for all three writers, who were, at the time, in their mid-twenties. At this point, Wordsworth was in a period of crisis, having recently returned from France, where he had fathered a child. Coleridge became intensely devoted to his friend: in his poem "To William Wordsworth," he refers to him as "my comforter and my guide!" Coleridge shortly afterward moved to the Wordsworths' native Lake District. In this period, the energetic Coleridge drew together a lively group of like-minded writers, and the two friends produced their most famous collaboration: the volume Lyrical Ballads. Some of each poet's most famous work appeared in Lyrical Ballads, and even as their styles differed—Wordsworth's focused on nature and solitude, Coleridge on dramatic, supernatural tales—they appeared to spur each other to new literary heights. Still, even at this point, conflicts emerged, among them Wordsworth's refusal to include certain works of Coleridge's in Lyrical Ballads.
Even at the height of their friendship, Wordsworth and Coleridge were known to be different in temperament. Wordsworth was considered the more diligent and introspective of the two, but was also known for rigidity and a formidable ego. Coleridge, meanwhile, was considered charmingly unpredictable and whimsical, but also self-destructive and undisciplined. Ultimately, the friendship soured as a result of these temperamental differences, as well as of personal crises external to the friendship. Coleridge developed a severe opium addiction and entered a disastrous marriage to Sara Fricker, made worse by the fact that he was infatuated with Wordsworth's sister-in-law. Meanwhile, the mentor-mentee dynamic that had characterized their early relationship came to seem, at least to Coleridge, like an unacceptable imbalance invited by Wordsworth's insatiable desire for admiration. The power imbalances that had once been a minor element of their friendship came to play a much larger role.
This was by no means an abrupt falling-out: after spending some time in the Mediterranean, Coleridge returned to England, and, with his own marriage in shambles, stayed at Wordsworth's home. Some of Coleridge's own writing about this time suggests that he witnessed—or hallucinated—Wordsworth in bed with Sara Hutchinson, his own sister-in-law and the object of Coleridge's obsession. This particularly lurid story is unproven, pieced together from cryptic diary entries and lines of poetry, but an underlying truth is clear: jealousy and suspicion had become major forces in this friendship. By the later years of their life, the two men were barely in contact, beyond a mutual involvement in similar social circles. Meanwhile, Coleridge expressed harsh opinions about Wordsworth's new work. Coleridge, meanwhile, is generally considered to have entered a severe decline, both artistically and personally, while Wordsworth became something of a political reactionary, turning on the radical politics both men had shared in their younger days. At the same time, these conceptions are somewhat unfairly dismissive—both writers continued to revise old work and create new work well into the nineteenth century, including, of course, the later revisions of The Prelude itself.
This broad history invites further speculation about the version of Coleridge portrayed in The Prelude. On the one hand, this version is evidently incomplete, not only because of Wordsworth's storytelling decisions but also because of the time at which it was written. Wordsworth completed the poem, for the most part, long before his friendship with Coleridge turned bitter. Certainly, the work's depiction of mutual affection, devotion, and collaboration matches up with the biographical facts of the friendship's early years. On the other hand, it is clear that the Coleridge of The Prelude is a literary device as much as a real person. Coleridge's presence on the page provides an audience stand-in and helps Wordsworth justify, within the text itself, his autobiographical project. Meanwhile, the version of Coleridge that exists within the poem is a helpful contrast and foil to the speaker, defining Wordsworth as much as Coleridge. In the end, the real-life relationship between Wordsworth and Coleridge and the literary friendship between their in-print alter egos is a complex one, drawn from life but distinct from it.