Fallacy of accident

No rule is so general, which admits not some exception. Fallacy of accident is a logical fallacy that occurs when a general rule (a rule of thumb or a "soft" generalization) is taken to be universal (an unconditionally true statement).

The fallacy is jumping to conclusions and an informal fallacy.

Alternate names

 * a dicto simpliciter ad dictum secundum quid
 * misuse of a principle
 * ignoring qualifications
 * sweeping generalization

Examples
Water boils at a temperature of 212° Fahrenheit; therefore boiling water will be hot enough to cook an egg hard in five minutes: but if we argue thus at an altitude of 5,000 feet, we shall be disappointed; for the height, through the difference in the pressure of the air, qualifies the truth of our general principle.


 * "Birds can normally fly" is a general rule, and doesn't imply that all birds (such as emus or penguins) can fly. To take this general rule and apply it to all birds would be committing a sweeping generalization.

Converse accident fallacy
Like many fallacies, simply flipping the logic used in the accident fallacy doesn't make it valid - you simply end up in another accident. The converse accident fallacy is committed when the speaker suggests that an overwhelming exception should become the new normal. It is related to the hasty generalisation. For example, suggesting that because asthma sufferers use inhalers to help them recover from attacks, everyone should be prescribed one to improve their breathing. Here, asthma sufferers are the exception.