There are more than two dozen fallacies in logic. As a writer, you should become aware that your reader may have critical thinking skills that will easily see any fallacy (or mistake in reasoning) in your logic arguments.
Fallacies in Logic Resources:
Some highly manipulative writers who have a very strong grasp of most of the major fallacies in logic exploit these to coerce their reader into believing one way of thinking. Example: Candidate X is so popular right now, he’s or she’s the best Presidential candidate for 2008. (bandwagon fallacy, that assumes you’ll support this candidate because he or she is the most popular rather than the best choice for the job).
I’m not certain that all fallacies in logic are ‘bad’, but a good student of logic should become very aware to identify when you’re either identifying a fallacy in logic that someone else wrote or you’re writing a bad reasoning fallacy in logic yourself without conscious awareness. Make sense?