Exception that proves the rule

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"The exception [that] proves the rule" is a frequently confused English idiom. The original meaning of this idiom is that the presence of an exception establishes that a general rule exists.

1 Original meaning
2 Popular meanings
3 References
4 External links

[edit] Original meaning

The phrase is derived from the medieval Latin legal principle exceptio probat regulam in casibus non exceptis ("the exception confirms the rule in cases not excepted"), a concept first proposed by Cicero in his defense of Lucius Cornelius Balbus.^[1] In other words, the fact that an exception is stated serves to establish the existence of a rule that applies to cases not covered by the exception. Fowler's Modern English Usage gives the following example:

"Special leave is given for men to be out of barracks tonight till 11.00 p.m."; "The exception proves the rule" means that this special leave implies a rule requiring men, except when an exception is made, to be in earlier. The value of this in interpreting statutes is plain.

Similarly, a sign that says "parking prohibited on Sundays" (the exception) "proves" that parking is allowed on the other six days of the week (the rule).

[edit] Popular meanings

In popular usage, the phrase is sometimes used to dismiss counterexamples to an overly broad assertion. For example:

"Bob is always late."
"That's not true. He was on time yesterday."
"Well, the exception proves the rule that he is always late."

This usage is illogical because the exception ("Bob was not late yesterday") is now directly contradicting the rule that it is claimed to support ("Bob is always late"), rather than demonstrating the existence of a rule that covers other cases.

The phrase may also be invoked to claim the existence of a rule that usually applies, when a case to which it does not apply is specially mentioned. For example, the fact that a nurse is described as "male" (the exception) could be taken as evidence that most nurses are female (the rule). This is a slightly looser interpretation of the original meaning described above.

It is sometimes said that the word "proves" means "tests", and that "the exception proves the rule" therefore means something like "an exceptional case can be used to test whether or not a rule is valid". This explanation is usually dismissed.^[2]