Most of us compare things all the time, at work, in school, and in everyday life. You might compare two people you know well, two motorcycles you are considering buying for a cross-country tour, three Stephen King novels, four tomato plants being grown under different laboratory conditions, or two theories about the relationship between inflation and wages. But as soon as you begin to compare two things, you usually begin to contrast them as well, for rarely are two things alike in all respects. The contrasts, or differences, between the two motorcycles are likely to be more enlightening than the similarities, many of which may be so obvious as to need no analysis. Comparison, then, brings similar things together for examination, to see how they are alike. Contrast is a form of comparison that emphasizes differences. According to research on learning, we acquire new concepts most readily if we can see how they are similar to or different from concepts we already know.
Professional writers say that comparison and contrast is a basic strategy they would not want to be without. Indeed, some writing is essentially extended comparison. But for all kinds of writing situations, writers regularly alternate comparison and contrast with other writing strategies when they present information.
Chances are that you will confront many test questions and essay assignments asking you to compare and contrast—two poems, three presidents, four procedures. This strategy is popular in all academic disciplines, for it is one of the best ways to challenge students intellectually. This chapter shows how you can organize a comparison/contrast, and it concludes with some sentence strategies you might use when comparing or contrasting.