exception proves the rule, the

‘The very fact of an exception proves there must be a rule’ (Brewer); now frequently misunderstood and used to justify inconsistency. Cf. L. exceptio probat regulam in casibus non exceptis, the exception confirms the rule in cases not excepted.

Exception strengthens the force of a Law in Cases not excepted.
[1640 G. Watts Bacon's Advancement of Learning viii. iii.]

I think I have sufficiently justifi'd the Brave man, even by this Reason, That the Exception proves the Rule.
[1664 J. Wilson Cheats A2^V]

There are a few passages which may pass for imitations, but so few that the exception only confirms the rule.
[1765 S. Johnson Shakespeare Preface C2^V]

As for the dictum about Temple Bar, why, the case of Poddle and Shaddery might be one of those very exceptions whose existence is necessary to the proof of every general rule.
[1863 W. S. Gilbert in Cornhill Mag. Dec. VIII. 727]

It is one of those cryptic sayings, like ‘The exception proves the rule’, which always puzzle me.
[1907 H. W. Fowler Si Mihi 80]

[H]ome was where most victims of murder met their end. This instance, he was prepared to concede, might just be the exception that proved the rule.
[1994 ‘C. Aird’ ‘Fair Cop’ in Injury Time (1995) 27]

Related to: rules, general

Bibliography of major proverb collections and works cited from modern editions is available here.

An instance that does not obey a rule shows that the rule exists. For example, John's much shorter than average but excels at basketball--the exception proves the rule. This seemingly paradoxical phrase is the converse of the older idea that every rule has an exception. [Mid-1600s]