They are most helpful when a writer is trying to explain something that is unfamiliar to his readers by explaining it in more familiar terms. Authors must compare two subjects carefully to ensure that they have essential features in common. Questionable analogies arise when a reader can point to one or more significant differences between the two subjects being compared in an analogy.
Historians often use analogies when comparing today s events to the past.
For example, attempting to equate the Vietnam War to the Persian Gulf conflict will quickly become problematic. If the differences outweigh the similarities, however, when making a comparison, then you have a contrast, not an analogy. Unfortunately, we do not have any one foolproof method of determining when analogies are legitimate or faulty. If the differences appear to be greater than the similarities then the analogy might be fallacious. Bear in mind that no single analogy is perfect, so this technique should be used only to illustrate foreign issues by placing them in common terms.