Leyendo SuperFreakonomics de Levitt y Dubner me crucé con este buen ejemplo de buena argumentación:
"When the world was lurching into the modern era, it grew magnificently more populous, and in a hurry.
Most of this expansion took place in urban centers like London, Paris, New York, and Chicago. In the United
States alone, cities grew by 30 million residents during the nineteenth century, with half of that gain in just
the final twenty years.
But as this swarm of humanity moved itself, and its goods, from place to place, a problem emerged. The
main mode of transportation produced a slew of the by-products that economists call negative
externalities, including gridlock, high insurance costs, and far too many traffic fatalities. Crops that would
have landed on a family’s dinner table were sometimes converted into fuel, driving up food prices and
causing shortages. Then there were the air pollutants and toxic emissions, endangering the environment as
well as individuals’ health.
We are talking about the automobile—aren’t we?"
"No, we’re not. We are talking about the horse.
The horse, a versatile and powerful helpmate since the days of antiquity, was put to work in many ways as
modern cities expanded: pulling streetcars and private coaches, hauling construction materials, unloading
freight from ships and trains, even powering the machines that churned out furniture, rope, beer, and
clothing. If your young daughter took gravely ill, the doctor rushed to your home on horseback. When a fire
broke out, a team of horses charged through the streets with a pumping truck. At the turn of the twentieth
century, some 200,000 horses lived and worked in New York City, or 1 for every 17 people.
But oh, the troubles they caused!
Horse-drawn wagons clogged the streets terribly, and when a horse broke down, it was often put to death
on the spot. This caused further delays. Many stable owners held life-insurance policies that, to guard
against fraud, stipulated the animal be euthanized by a third party. This meant waiting for the police, a
veterinarian, or the ASPCA to arrive. Even death didn’t end the gridlock. “Dead horses were extremely
unwieldy,” writes the transportation scholar Eric Morris. “As a result, street cleaners often waited for the
corpses to putrefy so they could more easily be sawed into pieces and carted off.”
The noise from iron wagon wheels and horseshoes was so disturbing—it purportedly caused widespread
nervous disorders—that some cities banned horse traffic on the streets around hospitals and other
And it was frighteningly easy to be struck down by a horse or wagon, neither of which is as easy to control
as they appear in the movies, especially on slick, crowded city streets. In 1900, horse accidents claimed the lives of 200 New Yorkers, or 1 of every 17,000 residents. In 2007, meanwhile, 274 New Yorkers died in auto
accidents, or 1 of every 30,000 residents. This means that a New Yorker was nearly twice as likely to die
from a horse accident in 1900 than from a car accident today. (There are unfortunately no statistics
available on drunk horse-drivers, but we can assume the number would be menacingly high.)
Worst of all was the dung. The average horse produced about 24 pounds of manure a day. With 200,000
horses, that’s nearly 5 million pounds of horse manure. A day. Where did it go?
Decades earlier, when horses were less plentiful in cities, there was a smooth-functioning market for
manure, with farmers buying it to truck off (via horse, of course) to their fields. But as the urban equine
population exploded, there was a massive glut. In vacant lots, horse manure was piled as high as sixty feet.
It lined city streets like banks of snow. In the summertime, it stank to the heavens; when the rains came, a
soupy stream of horse manure flooded the crosswalks and seeped into people’s basements. Today, when
you admire old New York brownstones and their elegant stoops, rising from street level to the second-story
parlor, keep in mind that this was a design necessity, allowing a homeowner to rise above the sea of horse
All of this dung was terrifically unhealthy. It was a breeding ground for billions of flies that spread a host of
deadly diseases. Rats and other vermin swarmed the mountains of manure to pick out undigested oats and
other horse feed—crops that were becoming more costly for human consumption thanks to higher horse
demand. No one at the time was worried about global warming, but if they had been, the horse would have
been Public Enemy No. 1, for its manure emits methane, a powerful greenhouse gas.
In 1898, New York hosted the first international urban planning conference. The agenda was dominated by
horse manure, because cities around the world were experiencing the same crisis. But no solution could be
found. “Stumped by the crisis,” writes Eric Morris, “the urban planning conference declared its work
fruitless and broke up in three days instead of the scheduled ten.”
The world had seemingly reached the point where its largest cities could not survive without the horse but
couldn’t survive with it, either.
And then the problem vanished. It was neither government fiat nor divine intervention that did the trick.
City dwellers did not rise up in some mass movement of altruism or self-restraint, surrendering all the
benefits of horse power. The problem was solved by technological innovation. No, not the invention of a
dung-less animal. The horse was kicked to the curb by the electric streetcar and the automobile, both of
which were extravagantly cleaner and far more efficient. The automobile, cheaper to own and operate than
a horse-drawn vehicle, was proclaimed “an environmental savior.”
Cities around the world were able to
take a deep breath—without holding their noses at last—and resume their march of progress.
The story, unfortunately, does not end there.
The solutions that saved the twentieth century seem to have
imperiled the twenty-first, because the automobile and electric streetcar carried their own negative
externalities. The carbon emissions spat out over the past century by more than 1 billion cars and
thousands of coal-burning power plants seem to have warmed the earth’s atmosphere. Just as equine
activity once threatened to stomp out civilization, there is now a fear that human activity will do the same.
Martin Weitzman, an environmental economist at Harvard, argues there is a roughly 5 percent chance that
global temperatures will rise enough to “effectively destroy planet Earth as we know it.” In some quarters—
the media, for instance, which never met a potential apocalypse it didn’t like—the fatalism runs even
This is perhaps not very surprising. When the solution to a given problem doesn’t lay right before our eyes,
it is easy to assume that no solution exists. But history has shown again and again that such assumptions are