Techniques of comparison (telling what's similar) and contrast (telling what's different) are techniques in writing description, analysis, and argument. Using comparison and contrast to develop your ideas enables you to weigh the relative merits of various items or ideas that you wish to consider. Suppose you want to determine which of two proposals will best solve a specific problem. By studying the advantages and disadvantages of each proposal, you can determine which would work best given various needs or concerns such as number of people involved, budget limitations, time frame, and so forth. Then, by weighing those factors based on your situation and your needs, you can reasonably choose the proposal that best serves the purpose. Presenting your choice in writing or orally is the next step, and you will want to show your analysis to your audience and persuade them that you made an accurate decision.

Using comparison and contrast within the form is easy. The structures you use in the form can easily accommodate similarities and differences that help support your thesis and explain the points in your projected organization. Make special note that a controlling idea or thesis is followed by supporting evidence structured into a "point by point" comparison or contrast or a "subject by subject" organization of similarities and dissimilarities. In other words, you could discuss each of the issues you present in your projected organization by explaining the comparisons and contrast within each of those points. Or, you can discuss all the similarities (included in all the projected issues) and then all the differences (again, included in all the projected issues). Thus, in the example of choosing a proposal discussed above, your essay or project report presents your conclusion as your thesis, and you use the points of your logical comparison and contrast to support that thesis.

When you use comparison and contrast techniques, you will want to observe and control the development of your text carefully. A comparison and contrast essay has a tendency, by virtue of its detailed one-side-or-the-other content, to become merely a list of similarities and differences. In other words, your essay may describe the similarities and differences rather than present your conclusion about them. Make sure that your thesis presents your conclusion about the factors you studied. Then, the body will support your conclusion by showing the reasons why you reached your conclusion. Thus, in our example about choosing a proposal, your conclusion, which is your thesis, claims that one proposal will solve the problem, and the body of your essay or report will show the reasons why that proposal was selected. Your essay presents your analysis of the issues and supports your conclusion.

Comparison and Contrast on the micro-level:

In addition to considering ways to use comparison and contrast as a method for development of your essay, you will want to consider more specific types of comparison,

especially analogies, metaphors, and similes. These stylistic devices help the readers connect bits of knowledge they already have with new information. Such devices allow you to bring your new ideas about relationships to your audience; you can make original connections that haven't occurred to the readers. By the same token, using contrasting ideas or images helps your readers recognize dissimilarities in things they thought were alike. We all tend to generalize, but knowing and showing where or how details cause differences give and us and our readers a clearer, more specific image of an action, item, or idea than might appear at first glance. And those details help us weigh relative merits of competing factors as we attempt to make choices.

Even if you don't use those stylistic devices, providing specific details enables you provide vivid images that help your reader grasp your intent. Consider the difference between "Gourmet cooks like to eat snails" and "Gourmet cooks like to eat pond-raised, flavorful, sweet tasting snails but not wild ones, which taste like muddy water." In the first case, you have a generalization about all gourmet cooks and one about all snails; in the second, the generalization about the cooks is still present, but you have refined the notion of snails by contrasting domestic and wild snails. Those details help us distinguish between wild and domestic, pond-raised snails, and perhaps help us determine which kind of snails we might like to eat. How could you eliminate the general reference to gourmet cooks?