Fallacy is an error in reasoning. Many fallacies appear persuasive and may lead people to false conclusions. Logicians (people who study logic) divide fallacies into two main groups, formal and informal.
A formal fallacy is an argument containing a faulty structure or form. The following incorrect argument is an example of a formal fallacy: Because only seniors have their pictures in the book, and because John is a senior, then John’s picture is in the book.
Informal fallacies are errors other than violations of the rules of formal logic. Logicians disagree about the number and kinds of informal fallacies. One informal fallacy, called hasty generalization, is the assumption that what is true of a few cases is true in general. The assumption that what is true of parts is also true of the whole is a fallacy based on a presumption or silent assumption. A fallacy of relevance is an argument in which the truth of the conclusion does not depend on the claims made by the premises (beginning statements).
