Related:

• Without exception, all infallible rules have an exception. -- Pickett's Infallible Rule
• There is no useful rule without an exception. -- Thomas Fulle
• O you much partial gods! Why gave ye men affections, and not power to govern them?
  -- Ludovick Barry...
• No experiment is ever a complete failure. It can always serve as a bad example, or the exception that proves the rule (but only if it is the first experiment in the series).
  -- Futility Facto...
• If for every rule there is an exception, then we have established that there is an exception to every rule.
  If we accept "For every rule there is an exception" as a rule, then we must conced that there may not be an exception after all, since the rule states that there is always the possibility of exception, and if we follow it to its logical end we must agree that there can be an exception to the rule that for every rule there is an exception....
• If for every rule there is an exception, then we have established that there is an exception to every rule.
  If we accept "For every rule there is an exception" as a rule, then we must concede that there may not be an exception after all, since the rule states that there is always the possibility of exception, and if we follow it to its logical end we must agree that there can be an exception to the rule that for every rule there is an exception....
• To rule is easy, to govern difficult. -- Goethe
• There is an exception to every rule, except this one.
• To every rule there is an exception, and vice versa.