Paul Krugman

It's true that scientists don't know exactly how much world temperatures will rise if we persist with business as usual. But that uncertainty is actually what makes action so urgent. While there's a chance that we'll act against global warming only to find that the danger was overstated, there's also a chance that we'll fail to act only to find that the results of inaction were catastrophic. Which risk would you rather run?

It wasn't so long ago that global warmists were acting as if their alarming forecasts had already come true, even likening skeptics to Holocaust deniers. Now they are reduced to saying we really don't know if global warmism is true or not, but since the consequences are so dire if it is, we'd better just assume that it is and act accordingly.

If this sounds familiar, perhaps you've heard of Pascal's Wager. Blaise Pascal, a 17th-century French theologian and mathematician, wanted a reason to believe in God but believed that God's existence could not be proved by reason. So he argued instead that faith was a good bet.

If you believe in God and you turn out to be right, Pascal argued, the payoff is "an infinity of an infinitely happy life." If the probability of God's existing is anything greater than zero, then, the expected value of the bet is infinity, and therefore the rational thing to do is bet on God.

Krugman is interested in hell, not heaven. If nonbelievers are wrong about global warmism, the results will be "catastrophic." Therefore, believing in global warmism is a good bet regardless of the actual probability that it is true.

One problem with Pascal's Wager is that assuming an infinite payoff is a cheat of sorts--one that renders calculations of expected value nonsensical. As the Stanford Encyclopedia of Philosophy points out, it turns out that flipping a coin and believing in God only if it comes up heads also yields an infinite expected value.

Krugman's Wager presumably does not presuppose an infinite expected value, but Krugman cheats in the same way. By raising the specter of "catastrophic" consequences, he evades the question of just how probable those results are.

Another problem with Pascal's Wager is that it presupposes only two possibilities: Either God exists more or less as Christians conceive of him, or he doesn't exist at all. But from a standpoint of pure logic, this is completely arbitrary. What if God exists and it is Muslims or Mormons or atheists who go to heaven?

Krugman's thinking is similarly binary: Either global warming is true and the stakes are enormous, or it isn't and they are trivial. But how do we know that global warming won't turn out to be beneficial, or that efforts to avert it won't have catastrophic consequences?

One difference between Pascal's Wager and Krugman's is that whereas Pascal was making a case for individuals to embrace faith, Krugman is arguing for collective action--which is to say, he wishes to use the power of government to impose his beliefs on others.

By imploring political leaders to make a bet on speculative predictions of catastrophe, Krugman has made an important concession: that current scientific knowledge is insufficient to justify the "action" he advocates. Seems to us it's more prudent to bet against the former Enron adviser.

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