A synthesis is a written discussion that draws on one or more sources. It follows that your ability to write syntheses depends on your ability to infer relationships among sources - essays, articles, fiction, and also nonwritten sources, such as lectures, interviews, observations. This process is nothing new for you, since you infer relationships all the time - say, between something you've read in the newspaper and something you've seen for yourself, or between the teaching styles of your favorite and least favorite instructors. In fact, if you've written research papers, you've already written syntheses. In an academic synthesis, you make explicit the relationships that you have inferred among separate sources.
The skills you've already been practicing in this course will be vital in writing syntheses. Clearly, before you're in a position to draw relationships between two or more sources, you must understand what those sources say; in other words, you must be able to summarize these sources. It will frequently be helpful for your readers if you provide at least partial summaries of sources in your synthesis essays. At the same time, you must go beyond summary to make judgments - judgments based, of course, on your critical reading of your sources - as you have practiced in your reading responses and in class discussions. You should already have drawn some conclusions about the quality and validity of these sources; and you should know how much you agree or disagree with the points made in your sources and the reasons for your agreement or disagreement.
Further, you must go beyond the critique of individual sources to determine the relationship among them. Is the information in source B, for example, an extended illustration of the generalizations in source A? Would it be useful to compare and contrast source C with source B? Having read and considered sources A, B, and C, can you infer something else - D (not a source, but your own idea)?
Because a synthesis is based on two or more sources, you will need to be selective when choosing information from each. It would be neither possible nor desirable, for instance, to discuss in a ten-page paper on the battle of Wounded Knee every point that the authors of two books make about their subject. What you as a writer must do is select the ideas and information from each source that best allow you to achieve your purpose.
Your purpose in reading source materials and then in drawing upon them to write your own material is often reflected in the wording of an assignment. For example, your assignment may ask that you evaluate a text, argue a position on a topic, explain cause and effect relationships, or compare and contrast items. While you might use the same sources in writing an argumentative essay as your classmate uses in writing a comparison/contrast essay, you will make different uses of those sources based on the different purposes of the assignments. What you find worthy of detailed analysis in Source A may be mentioned only in passing by your classmate.
USING YOUR SOURCES
Your purpose determines not only what parts of your sources you will use but also how you will relate them to one another. Since the very essence of synthesis is the combining of information and ideas, you must have some basis on which to combine them. Some relationships among the material in you sources must make them worth sythesizing. It follows that the better able you are to discover such relationships, the better able you will be to use your sources in writing syntheses. Your purpose in writing (based on your assignment) will determine how you relate your source materials to one another. Your purpose in writing determines which sources you use, which parts of them you use, at which points in your essay you use them, and in what manner you relate them to one another.