The Immutability of Concepts

Abraham Lincoln once commented, "How many legs does a dog have if you call the tail a leg? Four. Calling a tail a leg doesn't make it one." Lincoln was a great President but a lousy linguist. I think most linguists would agree that if all English speakers agreed to change the meaning of the word 'leg' to something more like 'appendage,' a dog's tail could be counted.

But Lincoln was no fool, so perhaps his comment means more than meets the eye (or ear). Although we could change the name for a tail, we cannot turn a tail into a leg. A tail would still lack the defining elements of a leg like a foot and claws or nails. We must be careful to divide the concept of a leg from its name. A name is arbitrary, a concept is timeless.

Of course, some concepts involve arbitrary elements. Consider the case of units of measurement. A 'foot' is an arbitrarily chosen length. In fact, the English and French both used 'feet' for measurement but an English foot was slightly shorter than its French counterpart--leading to a persistently stubborn myth about Napoleon's short stature. Napoleon's height was noted as 5 foot 2 inches. This measurement was in French feet (pieds de roi) and was never correctly converted to standard English measure. In English feet, Napoleon stood 5 foot 6.5 inches tall--slightly above average for his time.