A fallacy of accident is an informal fallacy in which a rule that includes exceptions is applied to a situation as though there were no exceptions to the rule. In other words, this fallacy occurs when a “rule of thumb,” which is created to include exceptions, is replaced with a universal generalization, which includes no exceptions. This type of fallacy can be attacked in an argument or debate by simply pointing out that the application of the rule is flawed and ignores noted or established exceptions to that rule. A fallacy of accident often occurs when someone attempts to use a cliché within an argument.
Also called a sweeping generalization, a fallacy of accident is typically the result of someone not fully understanding exceptions within a given rule. This can occur when someone does not first establish his understanding of a rule, to determine whether it is a rule of thumb or a universal generalization. A rule of thumb is a rule created to include exceptions, such as “All normal or typical dogs have fur.” In contrast to this is a universal generalization, which would be the statement “All dogs have fur,” which does not include any possibility of exceptions.
A fallacy of accident can occur when someone uses a universal generalization in a situation in which a rule of thumb would be more appropriate. In the previous example, the rule of thumb uses the words “normal or typical” to allow for situations such as dogs that do not naturally have fur, dogs that have been shaved, and dogs that are sick and have lost their fur. Someone arguing that a furless dog is not a dog, since it does not have fur, has committed a fallacy of accident by viewing the class of dogs through the universal generalization, which is obviously flawed.
When a fallacy of accident is used, it can be easy for someone to attack the argument by pointing out the fallacy. This can be done by simply indicating a known exception to the rule the person has stated as part of his or her argument, which invalidates the accident as the basis of the argument. In the example with dogs, someone arguing that all dogs have fur could be refuted by an opponent citing the American hairless terrier or any breed of poodle, which has hair instead of fur. Someone using a cliché, such as “You can’t make an omelet without breaking some eggs” is also committing a fallacy of accident. To refute such a claim, someone else need only disprove the cliché itself, or provide an example of a situation that goes against the meaning of the statement.