In 1670, four years after the death of the French philosopher and mathematician Blaise Pascal, his friends published a collection of his reflections under the title of Pensées. One of these reflections became known as Pascal's Wager.

During the last few years of his brilliant 39 years, Pascal agonized over the failings of both reason and belief as methods of determining truth because neither could eliminate uncertainty. God could not be known by reason, Pascal concluded, and reason itself was a process of understanding whose validity had to be accepted without the verification of an external proof. Given this dilemma, what was an honest seeker of truth to do?

Since neither reason nor belief could be trusted, Pascal finally decided, it is a better "bet" to believe in God than not to do so because the cost of believing in a God that may not exist is relatively small compared to the cost of not believing in a God that may exist. This consideration of costs against probabilities is Pascal's Wager. And it continues to be used today when we measure the consequences of inaction against action. A perfect example is provided by the present global financial crisis and the measures governments are taking to support monetary systems and economies.

A belief in capitalism and free-market economies should dictate that the present financial crisis will correct itself without government intervention. Faulty business practices will fail and be purged from the system, the regulating dynamics of supply and-demand will eventually return, confidence will recover as the system cleanses itself of defects, and economic health will re-establish in an improved form.

The problem is that neither economists nor politicians are certain that the system will right itself if they do nothing. And the social and economic costs of not intervening are extremely high, even though no one is certain that any amount of intervention will actually be corrective. So governments and economists, with the public's blessing, make Pascal's Wager. Even though the results are uncertain, intervention is a better bet than no intervention. Or, to paraphrase the Canadian philosopher and economist Thomas Homer-Dixon, "Do we reduce the likelihood of catastrophe by risking the loss of a little money or do we risk no money at a greater likelihood of catastrophe?"

The amount of money being risked to reduce the likelihood of a catastrophe has reached staggering sums. Barry Ritholtz, in his recent book, Bailout Nation, contends that the US Federal Reserve has "spent, promised, loaned, guaranteed or assumed in liabilities amounts that are now approaching $14 trillion" (Newsweek, Dec. 29/08) ‹ "Forget the numbers," suggested one economist, "just think infinity." Other countries are shoring up their financial institutions by trillions of dollars and their economies by hundreds of billions. America is planning indefinite annual budgetary deficits of at least $1.2 trillion. Canada's government, which vowed that its budgetary future would only entail surpluses, is planning a deficit budget that will likely be about $34 billion.

But none of these amounts will guarantee a solution to the financial crisis reverberating around the planet. In an uncertain world paralleling the one inhabited by Blaise Pascal in the 17 century, all this money will only reduce the risk of catastrophe. Which raises the uncomfortable subject of another impending catastrophe, our response to the risks involved, and what this reveals about our values and priorities.

Sir Nicholas Stern, a British economist with international credentials, was commissioned by his government to estimate the financial costs of measures that would avoid global warming. If not stopped, the resulting climate change could cause erratic and extreme weather, raise ocean levels high enough to displace hundreds of millions of people in cities and lowlands, obliterate about a third of the world's plant and animal species, devastate global agriculture production, induce mass starvation and dislocation, and wreck world economies ‹ just to mention the most obvious consequences. Compared to the $14 trillion America wagered in a few months to reduce the risk of a financial crisis, Sir Nicholas estimated that the world could fix the global warming problem by investing $9 trillion over the next 100 years.

Unfortunately, no one knows for certain if $9 trillion ‹ or even an infinite amount of money should we be too late for corrective action ‹ will rescue us from the looming environmental catastrophe of global warming. Like Blaise Pascal almost 350 years ago, we need to honestly examine our situation, consider our options, weigh the probabilities, then collectively and individually bet on the wisest action to minimize risk. The longer we delay, however, the higher the risk.

If our situation is being properly measured by the vast majority of today's most credible scientists, we are not wagering on the relative validity of belief or reason, or even on the stability of our economic system. At stake is the continued existence of human civilization and the natural world as we know it.

In the fiscally innocent days of 2006, before the global financial meltdown of 2008, $9 trillion also seemed like a staggering amount of money ‹ even by the measure of modern excesses. Now this amount, spread over a century, seems modest, even a bargain, considering the cost of doing nothing.