In the past decade the writing process was defined as three steps. 1) Prewriting 2) writing 3) rewriting but Murray change these three words to be 1) prevision 2) vision 3) revision.
Discovery meant to be inventive and have high imagination in writing, while Ignorance means almost the opposite meaning of Discovery
The process that Murray is talking about is the way in which we view the world, how we feel about it and how we convey that through language. We also invent the world through our perception of it. While the product is a traditional approach, in which students are encouraged to mimic a model text.
Internal revision is everything writers do to discover and develop what they have to say, beginning with the reading of a completed first draft. They read to discover where their content, form, language, and voice have led them…The audience is one person
External revision is what writers do to communicate what they have found to another audience…They eye their audience and may choose to appeal to it. They read as an outsider.