From Wikipedia: "the presence of an exception applying to a specific case establishes that a general rule exists." https://en.wikipedia.org/wiki/Exception_that_

From Wikipedia: "the presence of an exception applying to a specific case establishes that a general rule exists." https://en.wikipedia.org/wiki/Exception_that_proves_the_rule https://en.wikipedia.org/wiki/Exception_that_proves_the_rule The fact that the parent is complaining about a small number of exceptional cases proves that the system works well in the general case.