As you know, an essay is a “try” at arguing for or against a point of view. Often, an essay will “analyze” or examine the structure of something—for example, an essay that argues that sexual abuse in childhood is the cause of anti-social behavior in adulthood. But an equally effective use of the essay form of argument is the “synthesis” essay that, rather than take something apart to reveal it cause-effect relationship, blends or combines two heretofore unconnected items together, to “synthesize” (make something new by combining) a new observation. A literary example is Martin Esslin’s book-length essay Theatre of the Absurd. In it, he looks at the structure, themes, and language of several modern plays (Beckett’s Waiting for Godot, Ionesco’s “The Chairs,” etc.) and, seeing some similarities, synthesizes a new category, which he names “absurdist drama.” Because it is a synthesis essay, it can then be criticized or supported by further scholarship, and his argument can be looked ar for flaws, etc., just like any essay. (Many scholars, for example, objected to calling Godot an Absurdist play.) When you argue that your topic is a subset of a taxonomy, you are writing a synthetic essay. You are claiming that your examined objects share a group of traits inside their genre or category. A modern example might be when you argue that web sites should be classified not by their obvious topics, but by their language and information sophistication, you are making a “synthetic” argument, and you will support your argument by citing web sites (National Geographic, New York Times, and TED), giving them a name such as Mental Simulation sites, and grouping them accordingly.