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February 11, 2007

The Problems with the Precautionary Principle

I was watching a Penn and Teller piece on environmentalists, courtesy of the Jawa Report, and was struck anew by the fallacies embedded in the precautionary principle. I need to differentiate between Wikipedia's definition and the way that the precautionary principle is used in practice, even though both are wrong, and the Wikipedia's more reasonable-sounding definition in fact only sounds more reasonable.

Wikipedia says the precautionary principle states that "if an action or policy might cause severe or irreversible harm to the public, in the absence of a scientific consensus that harm would not ensue, the burden of proof falls on those who would advocate taking the action." The more common way of using the precautionary principle is to claim that if there is the possibility, no matter how remote, of harm being caused by action or inaction (on certain issues), then the action or inaction which might possibly cause harm cannot be done until the proponents of the action (or inaction) can prove that no harm will result.

The first fallacy is hidden in the unstated premise: those issues to which the precautionary principle may be applied are inevitably the issues of interest to anti-capitalists, anti-industrialists, socialists, environmentalists and the like. The precautionary principle is never applied by such people to problems such as, say, Iran, or jihadi terrorism, and indeed is rejected utterly in relation to issues not of interest to the radical Left.

The second fallacy is obvious: proof is not possible in science. All that you can do is build up evidence. But even overwhelming evidence falls immediately in the face of a single convincing counter-example. This is largely a problem with the Wikipedia definition, which stresses science and absolute terms. In the more common definition, the problem is worse: a veto is given to those on the correct (ie, more "progressive") side; until you prove to their satisfaction that you can act against their interests without causing harm, you must either do what they want, or not do what they do not want, depending on the issue. In other words, the precautionary principle is a way of stopping the argument in place: you cannot act because it might cause harm, and you cannot debate the point because we refuse to accept any evidence you might offer. Ergo, we win.

But there is a third and more insidious fallacy buried in the precautionary principle: there is no such thing as an absolute lack of harm. Every decision that we take, every thing that we do, causes harm in some measure to someone or something, particularly when we include those acts which we do not do. Let's take an easy example: if I spend money on environmental causes, that money is not available to feed my family, or prepare for my retirement. Now, an environmentalist might say that is true, but that the money spend on environmental causes does far more good for me (and if that argument fails, they will appeal to the greater good) than using my money for the other purpose. That would be a reasonable argument, and we could perhaps debate the point. They might even convince me in some circumstances. But the proponents of the precautionary principle implicitly exclude that cost-benefit analysis from issues to which the precautionary principle is applied. The precautionary principle sets the value of any level of harm at infinity, and the value of any countervailing cost at effectively zero. In other words, the precautionary principle assumes that any cost, no matter how massive, is worth creating a benefit, no matter how small or arguable.

What is left out of this consideration is the opportunity costs: what else could be done with the money? Let's say, for example, that the cost of fighting global warming is $10 trillion over some arbitrary unit of time. Let's further simplify by saying that global warming is happening, it is caused by humans, it will cause disastrous effects — let's assume as a single unit of measure 1 billion human deaths — if not stopped, and that spending that money will stop the warming and prevent the ill effects. Finally, let's discard even the possibility of natural causes of global warming, and assume that the climate does not change at all absent human causes. Now, here we are giving every arguable point (and more) to the proponents of anthropogenic global warming. So, why would we not, then, necessarily buy into the necessity of spending that money in that way?

What if we could prevent 2 billion deaths by spending $1 trillion over the same time period? That would leave another $9 trillion available for other uses, and would save additional lives besides. But the precautionary principle prevents any discussion of such tradeoffs, because it assumes infinite harm and zero cost, and so any discussion of using the resources available in different ways, even to the same end, is out of bounds: even if you save 2 billion lives, they are different lives, and that 1 billion might still die. In other words, a second line of argument-stopping "we win" assumptions is built into the precautionary principle.

But that in fact is the principle's power, and why it will continue to be made, even — in fact, particularly — in cases like global warming where there is a significant range of variation in possible outcomes and costs of action. That it is dishonest and fallacious does not appear in any way to enter the considerations of those who rely on the precautionary principle.

Posted by jeff at February 11, 2007 6:59 PM

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