The Exception Proves the Rule

The maxim is not an invitation to deny rationality.

At one time or another, most of us have thought of a counterexample when we heard someone overgeneralize or make an ideological statement as if it is a self-evident truth. If you point out the exception, the generalizer might dismiss it by smugly declaring “The exception proves the rule” instead of debating you.

But an exception doesn’t prove a rule. It might suggest the rule is wrong. Or it might just be an exception to a generalization that is true in most circumstances.

The Latin phrase Exceptio probat regulam in casibus non exceptis dates back to the Roman philosopher Marcus Tullius Cicero, a contemporary of Julius Caesar. It has been a principle of rhetoric for centuries, often poorly misunderstood and now echoed defensively by people who refuse to listen to a reasoned argument.

The idea is related to the dichotomy of explicit / tacit communication that I mention in another post. Namely, if you feel the need to state an exception, that implies there is already a rule in place, whether it is being mentioned by you or not.

A simple example that modern factory workers might find familiar:

“Employees do not have to wear uniforms on Fridays.”

The mention of one day of the week implies that a rule is in place on the other days.