Finally, there is an important distinction between a tentative and a definitive thesis. A tentative or working thesis is often valuable in the early stages of the writing process in that it guides your inquiry into your subject, suggesting questions, problems, and strategies. The best definitive theses, however, generally come late in the writing process. Hence, the writing process is not simply a means of codifying what you already know; it is a means of pushing beyond the commonplace, of exhausting the obvious, and of discovering what it is you ultimately want to say.
A good thesis, though essential to a good analytical essay, is not a panacea for sloppy exposition--there are scores of other things you must consider as you compose (such as style, syntax, organization, originality, punctuation, and diction). However, developing a thesis that is clearly expressed, adequately focused, well supported, and high in the orders of knowledge goes a long way toward ensuring the success of your essay.
REFERENCES
Adler, Mortimer. Dialectic. London: Kegan Paul, 1927.
Bloom, Benjamin, ed. Taxonomy of Educational Objectives: Handbook I. New York: David McKay, 1956.
Braddock, Richard. "The Frequency and Placement of Topic Sentences in Expository Prose." The Writing Teacher''''s Sourcebook. Ed. Gary Tate and Edward P. J. Corbett. New York: Oxford University Press, 1981.