When I comment on bad laws, and point out flaws by the approach of reductio ad absurdum, the usual response is that we must implement laws using "common sense". Now, this argument is faulty for a number of reasons, most notably that once a principle is allowed in law, it will run to its logical conclusion1, but for the moment let us limit ourselves to "common sense", as it is a topic I have written on several times2.
The problems with common sense are several, but all boil down to a very simple description, that being that if it were truly "common sense" we would not need to point it out or mention it. In other words, being "common" sense, we should all implement it already, without question. If we must debate it, if you must point out "common sense limits" and so on, then it is not "common", it is the position of some subset of humanity. And, if it is not universal, then how do we distinguish "common sense" from the bias, whim, prejudice or just personal values of the speaker? If I say common sense says there should be a minimum wage, how can you tell whether it is "common sense" or my own view?
And the problem is, you can't. There is no such thing as "common sense". If there were, as I said above, we would not need to mention it. Things that are common and automatic, as the assumed definition of "common sense" implies, we do not need to discuss. I don't have to remind you to breathe or eat or drink or use the bathroom. You need to do so, so do I, we do it without discussion or reminders. Common sense, if it truly existed, should be like that. As it is not, then what someone calls "common sense" is inevitably just something he sees as obvious, given his set of values and beliefs, but since neither of those is universal, is nothing like true "common sense" would be.
And, of course, that is assuming the speaker is being honest. Many times, "common sense" is not even what appears obvious to a speaker, but rather an expression of his wishes or biases, something he would like to have happen, but which he is aware is contentious even among those sharing his views and values.
I wrote this because I came across a perfect example of "common sense" diverging. In the US, we assume that people will generally eat something less than a perfect diet. And so, to avoid that problem, our government not only allows vitamins supplementation in food, but encourages it. Even mandates it in the case of folate. And for most people, this would probably be a matter of "common sense", if the foods we eat are likely to leave us vitamin deficient, then we should supplement them. And, if a few citiziens eat a more balanced diet, well almost all vitamins we supplement are water soluble, only a few could cause an overdose, and it is quite unlikely that would happen, so "better safe than sorry"3.
However, Denmark has actually done precisely the opposite, it has enacted laws mandating the opposite. Assuming its citizens receive sufficient vitamin intake from foods, they worry about overdose and ban foods with vitamin supplements4. If a few people might not get sufficient vitamins in their food, they can use supplements, but even the remote risk of overdose is worrisome, so "better safe than sorry".
As you can see, both approach a problem that can be argued either way. Granted, Danes and Americans eat differently, but the truth is, the risks involved are all somewhat small. As our wealth has increased, even "eating junk"5, our nutrition has improved incredibly over our ancestors. Yes, some less common nutrients, such as folic acid, may be somewhat deficient and supplements can have a benefit for some, but without supplements or with, true deficiency, as opposed to low levels with long term negative side effects, would be relatively uncommon. On the other hand, the risk of vitamin overdose from fortified foods is equally remote. Most vitamins which are fortified are water soluble, and those which are not take relatively large amounts to produce any sort of negative effect. (As with deficits, some may argue for long term effects of moderately elevated levels, but there is not a lot of evidence to back this up.) So, the "common sense" on both sides amounts to assessing one remote risk against another. However, US common sense and Danish completely disagree.
I grant, they are looking at different circumstances, but it is not as broad a difference as many think. US diets have, in general, improved greatly during the 20th and 21st centuries. For all the talk of "over processed"6 food and the like, we have a more diverse and more balanced diet than was common for the same social stratum 100 years ago. It is silly primitivism to imagine that city workers in the 19th century, or even farm hands, ate a better, more healthy diet than we do today7.But, regardless of the quality of the general US diet, there are many in the nation who eat a balanced diet, and have as great a risk of overdose as Danes do. Likewise, there are certainly Danes who eat poorly and would benefit from supplements, so both risks exist in both nations, making the divergence of "common sense" answers more striking.
Of course, the reason for this divergence is obvious. There is no "common sense" answer, as "common sense" is a fiction. Both nations enacted laws based on their own presumptions and biases, which they saw as "common sense", as every one of us tends to assume his beliefs are the standard of truth, the baseline against which other beliefs should be measured8. However, in truth, the decisions were no more "common sense" than all the decisions you made in the preceding week, or those I made. All decisions are the product of a personal values, and no set of personal values is so impeccable as to be deemed "common sense".
And thus, to claim we must use common sense to pass laws, or to limit some bad principle is to say we must cure one ill with another, we must base all future laws on some arbitrary set of values lest we go too far with a bad law9. And that seems a pretty bad way to create government policy.
1. The reason is obvious. As I have written in "Inescapable Logic", "Recipe For Disaster", "The Endless Cycle of Intervention" and "The Cycle of Compassion", the most consistent argument wins, and once a principle is allowed, the one which applies it most broadly is most consistent. So, even if the majority believes a principle should be taken only "so far", someone usually stands to benefit from a little wider application, and, being more consistent, will inevitably win their argument. Of course, someone else likely stands to benefit from an even wider implementation, and so takes it a bit farther still, and so on, and so on. And, in the end, we have Griswold allowing married couples to use condoms being mutated into Roe and arguments for unlimited access to publicly funded abortion. (Or to be less contentious, we have the commerce clause changing from a power to strike down interstate tariffs to Munn v Illinois which claims commerce exclusively within a state can be regulated because it "effects" interstate commerce.)
2. See "The Lunacy of "Common Sense"", ""Seems About Right", Another Lesson in Common Sense and Its Futility", "A Look at Common Sense", "Res Ipsa Loquitur", "The Shortcomings of Pragmatism", "Pragmatism Revisited", "Pragmatism Revisited, Again", "The Plural of Anecdote is Not Data", "Rules of Grammar and Pragmatism", "The Problem of the Small Picture", "Keyhole Thinking", "Impractical Pragmatists", "In Defense of Zero Tolerance, or, An Examination of Law, Common Sense and Consistency", "No Dividing Line", "The Consequences of Bad Laws" and "Questions of Law and Questions of Fact".
3. I have refuted "better safe than sorry" thinking in my essay ""Better Safe Than Sorry" Usually Leaves Us Even More Sorry, And Much Less Safe".
4. I also read a second theory, that foods with vitamin supplementation were mostly "junk foods" and so the Danes banned them to encourage "healthy eating". but as the articles I found were mostly about banning Marmite, Vegemite and the like, which are hardly traditional junk foods, that seems unlikely, though some may have based their decision on that assumption.
5. Considering the amount of starch eaten by our ancestors, claiming we eat a diet high in "empty calories" and "excessive carbohydrates" is absurd. When your main foodstuff is bread or porridge or grits, sometimes supplemented with some bacon grease, or maybe a bit of salt pork, with vegetables rare and fruits even more so, changing to the modern diet would seem a positive godsend, not to mention a health boon.
6. See "The High Cost of Not Wasting Food" and "In Defense of White Bread". Also "GMO? So What?", "A Misleading "Right to Know"", "Organic Absurdities" and "Irrational Environmentalism".
7. There were many in the 18th and early 19th century who noted the citizens of the US ate to excess, wolfed down huge amounts of mostly starches, and were regular users of patent remedies for gas and constipation. Vegetables were rare in many diets, as were fruits. So, it is a laugh to imagine our diet is somehow inferior to that of our ancestors. And comparing our middle class or lower class diet to a single example from say, Thomas Jefferson's diaries or some other uncommon individual of the upper classes is hardly a valid way to establish a decline in quality of food. See also "Mistaken Perceptions of the Industrial Age"and "Peaceful Matriarchies, Noble Savages and the Industrial Revolution". For my objections to primitivism in general, see "Primitivist Delusions",
"Rousseau's Foolish Legacy", "The Dishonesty of Avatar", "Happiness", "Opinion Masquerading as Fact", "A Western Evil?", "A Great Quote", "Stupid Quote of the Day (January 11, 2012)", "Contradictory Positions", "Deceiving Themselves?", "Stupid Quote of the Day (December 28, 2011)", "A Beast's Life" and "The Hunter-Gatherer Mistake".
8. Often this is a wholly unconscious practice. We are so familiar with our own beliefs and prejudices, we find them so self-evident, that we forget there are those who do not follow them. See "The "Liberal Bubble" Becomes Universal" and ""Nobody I Know Voted For Nixon"".
9. This is less clear than I had hoped. Basically, I am trying to combine the arguments of "The Consequences of Bad Laws" and "The Inherent Disappointment of Authoritarianism", if that makes sense.
For those who would ask "which do you favor?" I would answer "neither". The state should just stay out of the matter, and allow buyers and sellers to decide whether or not to supplement foodstuffs. If the supplements are in enough demand, then they will be sold. And, if they prove dangerous, well buyers will begin to avoid them, maybe even sue if the danger is a result of some actionable deed (such as supplementing to a toxic level in a single serving), and sellers will remove or change the level of fortification.
Allow me a small personal digression. Due to my ailments, I tend to avoid sunlight for the most part, and I am also not a milk drinker. As a result, I have a chronic vitamin D deficiency. Yet, unlike most of those "sick celebrities" who contract a disease and suddenly become advocates (and overnight experts), this does not make my clamor for supplements of D in ever substance known to man. Instead, I simply take it upon myself to take supplements and have my blood checked periodically. Problem solved. And all without massive government intrusion.
And, in the long run, I believe most people will resolve these problems in similar ways. Some will rely on fortified foods to get vitamins, some will eat a varied diet (with or without fortified foods), some will avoid "over processed' foods, some won't, some will take vitamin supplements, some won't, but in the end, all of us will do what we think best in terms of nutrition, and most of us will probably do pretty well. A few won't, but no law is going to save everyone, so to hold the free market to a standard of perfection is pretty absurd. (See "Third Best Economy" and "Government Quackery".)