Take a look at Aristotle's rhetoric. He gives a long list of type of enthymemes, various constructions of syllogisms arranged so that part is left out. It's been a long time since I looked at his impressive list, but I wonder who out there follows these kinds of persuasive constructions on purpose? I'd love to see a book that examines each of Aristotle's examples of enthymemes--a book that gives many contemporary examples of these uses. It would be something useful to study.