Audience is a crucial consideration in the convincing essay. If the purpose of this rhetorical strategy is to "make a case that readers can believe in" (Crusius 74), then you are under obligation to determine and overcome the objections your chosen audience will have about your claim. Be sure you are neither trying to accomplish the impossible (trying to convince a hostile audience of too much) nor preaching to the converted. Focus in the convincing essay is probably a matter of narrowness: are you trying to convince your reader that the population problem is the result of illiteracy? That is a huge claim to make and would require immense amounts of data to substantiate. If the writer narrows the claim to something like illiteracy in Kenya (where population growth is running about 4%) is a major contributor to the population problem there, has the writer made a more reasonable and focused claim? Make sure you have focused on an issue that is somehow related to human relationships with the environment. Development in the convincing essay might begin with defining the issue clearly enough that reader understands what the problem is. As we are relying solely on rational appeals ("hard" evidence and logic), development certainly has to do with providing evidence to support your claims and making sure that this evidence is valid. Beware of logical fallacies, the misuse of "facts," and those fuzzy areas among opinion, belief, and prejudice. Finally, a thoroughly developed piece will raise the counter-arguments of the intended audience and effectively refute those. Coherence in the essay is strong organization: among other things, transitions should be smooth; all the points should relate to the thesis; and readers should be able to see when the writer is presenting a counter-argument and when he or she is refuting it. Don't underestimate the potential for a using a strong voice in the convincing essay: by letting the audience know why you are personally concerned with the issue, you can increase your credibility as a writer and allow the reader to see why the issue might be an important one to consider.