To cut to the chase: because doing otherwise is a great waste of time and money, as well as fraught with the risk of shackling oneself risibly to the quantitative fallacy.

Allow me to quote from David Hackett Fischer’s Historical Fallacies: Toward a Logic of Historical Thought (Harper Colophon, 1970):

There is an epigram, perhaps apocryphal, attributed to Lord Kelvin, that everything which exists, exists in quantity. Enthusiastic quantifiers have amended Lord Kelvin’s statement to read, “Unless a thing can be measured quantitatively, it does not exist significantly.” Therein lies a fallacy.

There are many significant things in the world today that nobody knows how to measure. Someday, maybe, somebody will. But in the meantime one must acknowledge their existence. Many ideational and emotional problems, which lie at the heart of historical problems. cannot be understood in quantitative terms. To move to the periphery, because things can be measured there, is to behave like the man in Abraham Kaplan’s parable.

“There is a story,” Kaplan writes, “of a drunkard searching under a street lamp for his house key, which he had dropped some distance away. Asked why he didn’t look where he had dropped it, he replied, ‘It’s lighter here!'”

Longtime LR readers will remember my amusement at amended-Kelvinesque finding, which I dubbed “Well DUH research“: research projects to attract federal grant money to prove the patently evident. Examples include these by-now quantified propositions:

My favorite spoof of such research was a comedy skit in which a researcher is asked what he learned from many years of researching monkey torture, and he answers, “They hate it. The whole being tortured thing. Drives them nuts.”

The EU, however, shows the risk of such research extends beyond wasting time and money to endangering good sense. It goes from amended Kelvinism into a full-blown Kaplan’s drunk fallacy:

Brussels bureaucrats were ridiculed yesterday after banning drink manufacturers from claiming that water can prevent dehydration.

EU officials concluded that, following a three-year investigation, there was no evidence to prove the previously undisputed fact.

Producers of bottled water are now forbidden by law from making the claim and will face a two-year jail sentence if they defy the edict, which comes into force in the UK next month.