What is revision?
The transitive verb "revise" means "to look over again in order to correct or improve" (Webster's Ninth Collegiate Dictionary).
Why should you revise?
to clarify your thoughts.
(to find inconsistencies, information gaps, and poorly developed ideas.)
to communicate effectively with the reader.
(to reduce the reader's effort.)
(to increase the chances that he or she will read your paper.)
to modify your writing style.
(to meet your reader's expectations.)
(to satisfy your own stylistic and ethical standards.)
First drafts of papers almost always require revision because:
sentences are unclear or wordy;
adjacent sentences do not logically connect to each other (cohesion is poor);
paragraph topics are poorly defined (coherence is poor);
there are grammatical errors;
needed information is missing and unneeded information is not;
sentences and paragraphs lack rhythm, flow, and emphasis.
We often start revising by rearranging words in sentences (because sentences are easier to fix than paragraphs) but we cannot expect to focus only on sentences and then only on paragraphs and then only on logic. Changes in a sentence will often require other changes in the paragraph structure and vice versa, and so we must move from one level and site of repair to another. Consequently, writing well (revising, thinking) is hard work.
At the level of the sentence, we want the subject and verb to be close together and we usually want the verb to be in active voice. We want to eliminate needless words, needless abstraction, needless prepositional phrases. See revising sentences.
For paragraphs, we want adjacent sentences to connect to each other, i.e., we want a logical flow of ideas. And we want all sentences in one paragraph to relate to one clearly defined topic. See revising paragraphs.
Grammatical errors should be fixed because we want knowledgeable readers to recognize our writing for its logic and grace rather than for its errors. Moreover, incorrect grammar often contributes to illogical and or imprecise writing. When we fix the grammar, we fix the logic (or clarify that the writing is illogical) and highlight the imprecision. See other common problems.
As we streamline sentences and increase cohesion and coherence, we often find that some important elements are missing and that other elements should be deleted. Determining what is missing and what should go is difficult in the first draft because the important idea and supporting logic are often buried or absent. Only by revising can we bring the idea and logic into the open.
Finally, we recognize that even though our paper will not be read out loud, it will be easier to understand if the sentences and paragraphs have rhythm and emphasis.