A fallacy of reasoning is basically a flaw in an argument someone makes based on the logical structure of the argument itself. There are many different types of fallacies of reasoning, as this is a large category often used to indicate that the fallacy exists as a function of the logic within the argument itself. Common examples of this type of fallacy include begging the question, generalizations, and slippery slope fallacies. A fallacy of reasoning can also consist of a number of other fallacies, including a straw man argument and ad hominem attacks or arguments.
Also called an informal fallacy, a fallacy of reasoning occurs within informal logic, which utilizes structural concepts over mathematical formulas to deduce the strength of an argument. This type of fallacy typically occurs because some aspect of the logic within an argument is inherently flawed so the argument is then considered weak or unsupported. Such a fallacy of reasoning does not mean that the point a person is trying to make is true or false, but merely indicates the strength of the argument itself and how well supported it is.
There are many different ways in which a fallacy of reasoning can be created, such as begging the question. Also known as circular logic, begging the question occurs when someone uses the idea he or she is supporting as support for the argument itself. An example would be the statement, “Burglary is wrong because stealing is immoral,” because the person making the statement uses what he or she is trying to prove as proof.
Generalizations and slippery slope fallacies often occur when someone attempts to use data to support an argument in a flawed way. A generalization usually occurs when someone has a small amount of information or a small sample of a population and extrapolates that information to a much larger context than is appropriate. Slippery slopes typically happen when someone creates a causal connection between two ideas or events that are not directly linked by any demonstrable data or logical argument.
Other common types of fallacy of reasoning include a straw man argument. This fallacy occurs when someone attacks a weak or irrelevant aspect of an argument made by someone else, rather than the actual point of the argument itself. For example, if someone said “Guns need to be legal for people to protect themselves,” then a straw man argument might take the form of “Guns are used by criminals to kill others, so guns are dangerous and should be illegal.” This argument does not address the actual statement made by the first person, so is fallacious and does not strengthen the position of the second person.
Such arguments are similar to another type of fallacy of reasoning, known as an ad hominem attack or argument. This type of attack seeks to discredit the person making an argument, rather than addressing the argument itself. If a convicted criminal was arguing for more lenient sentences for people convicted of minor drug possession, someone against this idea might point out character flaws in the convicted criminal rather than addressing the actual merits or flaws of his or her ideas.