On Jean-Paul Sartre's What is Literature (1948), ch. 1 and 2.
What's the purpose of literature? Why write prose as opposed to poetry? Sartre argues that while poetry is about the words themselves, prose is about the ideas, so it's necessarily political. A written work is essentially an ethical appeal for a reader to apply his or her own faculties and experiences to complete the work through the act of reading.
The Partially Examined Life Philosophy Podcast