from http://everydaylife.globalpost.com/write-good-argumentative-essay-introduction-13297.html
To compose a thesis that is precise and well developed, read it to yourself and make certain it answers the questions "so what," "how" and "why." For example, the thesis "Big cars are bad for the environment" is too broad. How are big cars bad? And why does it matter? A more effective thesis statement would be, "Big cars harm society and the environment because they are costly and dangerous to smaller vehicles on the road, and they further America's dependency on foreign oil."
Thesis Statement
Your entire essay centers around your thesis statement. For an argumentative essay, your thesis statement will be one of three types of claims. In a claim of definition, you challenge the accepted truth of a fact. A cause-and-effect claim proposes that one action or event caused another. Another option is to propose a solution to a problem. The thesis statement is one sentence that must be debatable, but narrow enough in scope to prove within the constraints of the essay. Your thesis statement may evolve as you're writing, so check during the revision process to ensure it still relates to your arguments.
from http://classroom.synonym.com/write-good-argumentative-essay-introduction-2196.html
