How does Coleridge define the nature and function of poetry in Biographia Literaria?

In chapter 14 of the Biographia Literaria, Samuel Taylor Coleridge provides criteria for the definition of a poem and of poetry. He comments on the qualities contained in a poem, such as rhyme or meter, and then notes that any given work that contains these elements may be considered a poem, depending on the perspective of its reader, even if Coleridge or another person might disagree. Much depends on the writer’s intention and on the spirit that the reader derives from reading the work.

Nevertheless, defining a poem is not the same as defining poetry. Poems need not utilize meter, Coleridge notes. Poetry has a quality that excites “a more continuous and equal attention than the language of prose.” To define poetry requires considering what a poet is. This

is a distinction resulting from the poetic genius itself, which sustains and modifies the images, thoughts, and emotions of the poet's own mind.

Through the “poetic genius,” the poet’s charge is to engage the human soul by applying a “synthetic and magical power” that Coleridge calls “imagination.” It is a power revealed in the balance of opposites, as sameness is reconciled with difference. Here Coleridge names the general and the concrete, idea and image, and individual and representative. Poetry thus brings a freshness into the familiar, and engages an unusual state of emotion. Poetry must blend the natural with the artificial as it subordinates art to nature.

In chapter 15, he applies these elements to his analysis of William Shakespeare’s “Venus and Adonis.” After reviewing specific achievements in that poem, Coleridge links the work to his definition:

poetry is the blossom and the fragrancy of all human knowledge, human thoughts, human passions, emotions, language.

How does Coleridge view poetry as a form of knowledge in Biographia Literaria?

I think that Coleridge does view poetry as a source of knowledge.  One of Coleridge's primary points is the idea that poetic analysis and poetic expression can represent a way in which one knows the world around them.  Coleridge makes the point that the poetic exploration of the individual allows them to better understand the nature of themselves and their world.  Poetry is seen as something that is reflective of both the individual components of the world as well as the world itself.  In this pivot to bridge subjective and external perceptions of reality, Coleridge makes it clear that poetry can be seen as a form or mode of knowledge.  Coleridge understands clearly that the idea here is to explore the poetic form or mode as a way to perceive and to understand reality.  In this construction, it is evident that poetry is not dismissed as something trivial.  It can bring greater understanding towards what is understood and perceived and what can be gained in a larger sensibility.  Through such an idea, Coleridge is able to fully grasp how poetry is a mode of knowledge and a reservoir through which greater understanding can emerge.