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How Does an Exception Prove a Rule?

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Here are a few things that have recently been called “the exception that proves the rule”: the Mini-Transat sailing race  (because it’s international and doesn’t “boil down to duels between French sailors”), Adrian Peterson (because his success as a football player is not about “opportunity and scheme” but unusual talent), and a congressional compromise on student loans (because a congress reached a compromise!). Taken as a set phrase, “the exception that proves the rule” indicates a deviation from the norm, a challenge to the stereotype. It says, in effect, the norm or stereotype is the rule and here is something that is an exception to that rule. But wait, how does the exception prove the rule? Wouldn’t it do just the opposite? Doesn’t it prove that the rule does not hold for all cases and is therefore not a rule at all?

It is sometimes argued that the confusion over this expression stems from the wrong understanding of “prove,” that “prove” here means “test,” as in “proving ground” or a printer’s proof. The idea is that the exception tests the validity of the rule, and that test could either leave the rule intact (if some kind of explanation can be found) or overturn it. However, it’s hard to come up with an example where that is truly what is intended by the phrase. It almost always carries the assumption that the rule remains intact.

In fact, the “prove” part of the phrase was not very important in its original formulation. The expression comes from the Latin legal principle exceptio probat regulam (the exception proves the rule), also rendered as exceptio firmat regulam (the exception establishes the rule) and exceptio confirmat regulam (the exception confirms the rule). The principle provides legal cover for inferences such as the following: if I see a sign reading “no swimming allowed after 10 pm,” I can assume swimming is allowed before that time; if an appliance store says “pre-paid delivery required for refrigerators,” I can assume they do not require pre-paid delivery for other items. The exception here is not a thing but an act of excepting. The act of stipulating a condition for when something is disallowed (or required), proves that when the stipulated conditions do not hold, it is allowed (or not required). The general rules are that swimming is allowed before 10pm and that pre-paid delivery is not required. The fact that exceptions to those rules have been stated confirms those rules hold in all other cases. The full statement of the principle reads exceptio probat regulam, in casibus non exceptis. The exception proves the rule in cases not excepted.

These days, you’d have to be one heck of a stickler to insist that “the exception that proves the rule” only be used in its original Latin sense. It has probably come to its current sense through some blending with the expression, “every rule has an exception.” Most of the time, when people say something is “the exception that proves the rule,” they could just as well say it’s “an exception to the rule.” I would argue, however, that “the exception that proves the rule” does more by highlighting the unusualness of the exception. The Mini-Transat, or Adrian Peterson, or a Congress reaching an agreement are not just outside the norm, they are so far outside the norm they force you to notice what the norm is, or that there is one at all. There is an important kernel of the original sense here. The existence of the exception gives force to the rule. The no swimming after 10 pm sign makes it clear that it’s okay to swim before that. The congressional compromise on student loans makes it all the more clear that congress can’t compromise on anything else. Sure, there’s usually a good bit of hyperbole going on when someone pulls out this expression, but that doesn’t mean it doesn’t make any sense.

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Big Questions
What's the Difference Between Gophers and Groundhogs?
Gopher or groundhog? (If you chose gopher, you're correct.)
Gopher or groundhog? (If you chose gopher, you're correct.)
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Gophers and groundhogs. Groundhogs and gophers. They're both deceptively cuddly woodland rodents that scurry through underground tunnels and chow down on plants. But whether you're a nature nerd, a Golden Gophers football fan, or planning a pre-spring trip to Punxsutawney, Pennsylvania, you might want to know the difference between groundhogs and gophers.

Despite their similar appearances and burrowing habits, groundhogs and gophers don't have a whole lot in common—they don't even belong to the same family. For example, gophers belong to the family Geomyidae, a group that includes pocket gophers (sometimes referred to as "true" gophers), kangaroo rats, and pocket mice.

Groundhogs, meanwhile, are members of the Sciuridae (meaning shadow-tail) family and belong to the genus Marmota. Marmots are diurnal ground squirrels, Daniel Blumstein, a UCLA biologist and marmot expert, tells Mental Floss. "There are 15 species of marmot, and groundhogs are one of them," he explains.

Science aside, there are plenty of other visible differences between the two animals. Gophers, for example, have hairless tails, protruding yellow or brownish teeth, and fur-lined cheek pockets for storing food—all traits that make them different from groundhogs. The feet of gophers are often pink, while groundhogs have brown or black feet. And while the tiny gopher tends to weigh around two or so pounds, groundhogs can grow to around 13 pounds.

While both types of rodent eat mostly vegetation, gophers prefer roots and tubers (much to the dismay of gardeners trying to plant new specimens), while groundhogs like vegetation and fruits. This means that the former animals rarely emerge from their burrows, while the latter are more commonly seen out and about.

Groundhogs "have burrows underground they use for safety, and they hibernate in their burrows," Blumstein says. "They're active during the day above ground, eating a variety of plants and running back to their burrows to safety. If it's too hot, they'll go back into their burrow. If the weather gets crappy, they'll go back into their burrow during the day as well."

But that doesn't necessarily mean that gophers are the more reclusive of the two, as groundhogs famously hibernate during the winter. Gophers, on the other hand, remain active—and wreck lawns—year-round.

"What's really interesting is if you go to a place where there's gophers, in the spring, what you'll see are what is called eskers," or winding mounds of soil, Blumstein says [PDF]. "Basically, they dig all winter long through the earth, but then they tunnel through snow, and they leave dirt in these snow tunnels."

If all this rodent talk has you now thinking about woodchucks and other woodland creatures, know that groundhogs have plenty of nicknames, including "whistle-pig" and "woodchuck," while the only nicknames for gophers appear to be bitter monikers coined by Wisconsin Badgers fans.

Have you got a Big Question you'd like us to answer? If so, let us know by emailing us at bigquestions@mentalfloss.com.

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Big Questions
Why Does Santa Claus Give Coal to Bad Kids?
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The tradition of giving misbehaving children lumps of fossil fuel predates the Santa we know, and is also associated with St. Nicholas, Sinterklaas, and Italy’s La Befana. Though there doesn't seem to be one specific legend or history about any of these figures that gives a concrete reason for doling out coal specifically, the common thread between all of them seems to be convenience.

Santa and La Befana both get into people’s homes via the fireplace chimney and leave gifts in stockings hung from the mantel. Sinterklaas’s controversial assistant, Black Pete, also comes down the chimney and places gifts in shoes left out near the fireplace. St. Nick used to come in the window, and then switched to the chimney when they became common in Europe. Like Sinterklaas, his presents are traditionally slipped into shoes sitting by the fire.

So, let’s step into the speculation zone: All of these characters are tied to the fireplace. When filling the stockings or the shoes, the holiday gift givers sometimes run into a kid who doesn’t deserve a present. So to send a message and encourage better behavior next year, they leave something less desirable than the usual toys, money, or candy—and the fireplace would seem to make an easy and obvious source of non-presents. All the individual would need to do is reach down into the fireplace and grab a lump of coal. (While many people think of fireplaces burning wood logs, coal-fired ones were very common during the 19th and early 20th centuries, which is when the American Santa mythos was being established.)

That said, with the exception of Santa, none of these characters limits himself to coal when it comes to bad kids. They’ve also been said to leave bundles of twigs, bags of salt, garlic, and onions, which suggests that they’re less reluctant than Santa to haul their bad kid gifts around all night in addition to the good presents.

Have you got a Big Question you'd like us to answer? If so, let us know by emailing us at bigquestions@mentalfloss.com.

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