What are the differences and clashes between Wordsworth and Coleridge according to Biographia Literaria?

Coleridge, in Biographia Literaria, differs with his friend Wordsworth chiefly about the appropriate kind of language to use when writing poetry.

In his Preface to Lyrical Ballads, Wordsworth expresses the view that the language of poetry should essentially be no different from that of prose (allowing, of course, for the purely technical fact that poetry possesses meter and rhyme). Wordsworth therefore views with disfavor a specific kind of "poetic diction," or special words and expressions traditionally used in verse. He quotes Thomas Gray's "Sonnet on the Death of Mr. Richard West," considering such lines as "In vain to me the smiling mornings shine / And reddening Phoebus lifts his golden fire" as stilted and valueless. For Wordsworth, poetry must use a simpler kind of English, especially the language of people from the countryside.

Wordsworth's plan was basically to effect a revolution in poetry. Though it's sometimes necessary to make sweeping changes in order to start a new movement—in this case what we know as Romanticism—Wordsworth perhaps went too far. It's easy to see why Coleridge, though he collaborated with Wordsworth on Lyrical Ballads, would disagree with him on this point. The poem Coleridge is chiefly known for today is, of course, The Rime of the Ancient Mariner. Though simple and straightforward in its language, the poem uses deliberate archaisms and a style reminiscent of the folk ballad, not the sort of wording that we would see in, say, an essay or a novel.

In Biographia Literaria, Coleridge attempts to explain why the ideal poetic language cannot be dependent on the rigid prescription given by Wordsworth. For Coleridge, there is nothing especially superior or preferable about either prose-like diction or the language of rural people. What makes a poem great is independent of such factors.

What are Coleridge's major contentions with Wordsworth in Biographia Literaria?

A considerable portion of Samuel Taylor Coleridge’s Biographia Literaria is devoted to the critique of William Wordsworth’s ideas, which he presented in his Preface to Lyrical Ballads in 1800. Coleridge and Wordsworth were contemporary romantic poets and also good companions. Together, they wrote Lyrical Ballads in 1798, which is considered to pioneer the Romantic Movement in England. Coleridge admired Wordsworth and considered him to be one of the best poets of his generation, but he also disagreed and diverged from him on many points.

Coleridge developed his own theories about imagination, nature of poetry, poetic composition, etc. in Biographia Literaria, which are regarded as a very significant piece of literary theory and criticism.

According to Wordsworth, "nature" is the ultimate source of inspiration for creating poetry. He claimed poetry to be “the spontaneous overflow of powerful feelings…it takes its origin from emotion recollected in tranquility” and poetic diction or the language of poetry as the language of the “common man”. He even believed that there was essentially “no difference between language of prose and that of poetry”. He shunned the use of a lofty and elevated poetic diction.

Coleridge, however, did not agree with Wordsworth on his take on source of poetry as well as on poetic diction and meter. Coleridge relied on strong imagination as the source for creating great poetry. He also talked at length about primary and secondary imagination as well as fancy. For Coleridge, there ought to be a difference in language of prose and metrical composition, and they were strictly not identical. Coleridge, moreover, believed that low form of diction reflected poor poetic genius and vocabulary. He also questioned Wordsworth’s practice of his own theory of art. He said Wordsworth’s poetry shows conscious and reflective creation, which was at odds with his theory. Coleridge also differed from Wordsworth in explaining the origin of the idea of Lyrical Ballads. While Wordsworth took up natural scenes, he created poetry that took supernatural themes. Besides this, Wordsworth's claims of his choice of only rural, rustic life in creating art also found disagreements from Coleridge. Coleridge pointed out that not all of Wordsworth’s characters were essentially low and rustic. Besides, their appeal was not due to their rustic occupations, but because of the sentiments and character behind them, and these would have been the same had they been urban and not rural. Coleridge also agreed with Aristotelian concept of universal and representative characters. In later chapters, Coleridge also listed instances of Wordsworth’s poetic defects as well as his poetic excellences.