Would environmentalists argue that we need to learn more about this risk before acting? Almost certainly not. It’s safe to say that environmentalists would argue that “the precautionary principle” demands that, in the face of uncertainty, we assume the worst about this threat.

Environmentalists have, after all, vigorously crusaded against environmental health risks that range as high as 1‐​in‐​1‐​million and have been willing to spend several billions of dollars to save one statistical life. They have, moreover, militantly opposed any requirement that environmental risk reduction efforts be subjected to cost‐​benefit or risk‐​risk analyses. So it’s probably safe to say that the Greens would launch the political equivalent of a holy war against this environmental pollutant.

Would they be right to do so? Well, substitute the phrase “environmental pollutant” with the phrase “Saddam Hussein” and you’ve actually got a reasonably fair depiction of the debate about whether the United States should preemptively strike Iraq to prevent chemical, biological, or even nuclear weapons from falling into al Qaeda’s hands.

Risk is risk. Whether we’re talking about the risk of global warming or the risk of being subject to a nuclear attack, the fundamentals about how we should think about risk and how we should go about dealing with it shouldn’t vary based upon the particular risk at hand. If we are to take Greens seriously about how we should approach risk in the environmental arena, why shouldn’t we use their decision‐​making template when confronting other sorts of risks?

It’s worth noting, however, that absolutely nobody engaged in the debate about war with Iraq — even the environmentalists! — would dream of applying the environmentalists’ approach to risk assessment. Hawks and doves both accept that there are great uncertainties; that risks abound both in action and inaction; and that not undertaking cost‐​benefit and/​or “risk‐​risk” tests would be madness. The “precautionary principle” could cut either way and is accordingly useless.

Why do we think one way about environmental risks but another about public risks in other contexts? Or to put it another way, why do some of us have far greater tolerances for some risks (like getting nuked by bin Laden because he got the bomb from Saddam Hussein) but not for others (like getting cancer from PCBs because you ate too many fish from the Hudson)?

For no reason that we can see. The science behind many of the environmental risks we worry about, after all, is no more certain than the geopolitical calculations used to justify war or peace. The cost‐​benefit calculations are just as tough.

This isn’t to say that we should or should not launch a war against Iraq. It is to say, however, that the decision framework employed by environmentalists would look absurd in any other policy context if it were stripped of its emotional baggage. To focus only on the benefits of action rather than on both the costs and benefits of action, as well as inaction, is logically indefensible whether we’re talking about our war against terrorism or our war against pollution.