$700,000,000,000 (that's a lot of zeroes)

WHY IS $700,000,000,000 (looks bigger that way, doesn't it?) the particular number that's needed to restore investor confidence and fix the mess that investment banks and mortgage brokers have gotten us into? Good luck finding a convincing explanation.

The number, to quote Treasury Secretary Henry Paulson, needed to be "bold," big enough to "unclog the financial markets" but not unduly spook legislators who have felt the wrath of Main Street.

Why do we often find such numbers so convincing, even while recognizing, if only tacitly, how arbitrary they are? Numbers accumulate their authority much as other forms of knowledge become credible, and we know from experience that accuracy does not necessarily prevail. Numbers get bandied about. Different interest groups embrace different figures. New groups find new uses that extend their influence. Numbers become a shorthand for complex situations and processes.

Earlier estimates for the bailout ranged from $500 billion to $1 trillion (a number that has vanished faster than home equity). So $700 billion is a political compromise. But does anyone really know how to budget for this mess?

Of course not. The costs are impossible to quantify. No one knows how many virtually worthless securities are out there and it doesn't help if the SEC keeps changing the rules about how to value them. No one knows how many of them the government will have to buy or if they will be worth anything when they "mature." We may not know for years what the real cost of the bailout will be. But $700 billion looks like you're trying hard. The whole world is scrutinizing just how fragile and unregulated our financial markets are. And no one knows if it will work.

But more of us are realizing that we have do something, even as we strongly suspect that if things don't pan out, the big losers will not be the banks who made the reckless investments or the few failed executives whose golden parachutes won't be inflating.

Politicians know they need a number that people can rally around. If the government doles it out in pieces - $250 billion plus $100 billion plus $350 billion - it is going to be less gag-worthy than $700 billion, even if the oversight and timetable for that sequence is less than clear. That's the thing about a lot of big numbers: they are always less transparent than they seem. All the premises, discretion, mistakes, and biases that went into their production are much harder to retrieve once a big number starts moving around, gathering people with a stake in it.

The further numbers travel from people who remember how they were made, the more they get talked about as "the" number rather than "a" number, the more real and powerful they become. The editing that gets done around important numbers makes their precision seem apparent, their vulnerabilities less obvious. Our attention shifts, and not just in how we think about a particular number, but in how we think about the issue the number is designed to solve or illuminate.

Just like other kinds of "facts," a number like 700 billion can take on a life of its own. This is not necessarily a bad thing. We need to simplify complicated issues in order to talk about them and we cannot endlessly debate everything. But we should be wary of investing any more authority in numbers than they deserve, of being taken in by precision that is only apparent, or in thinking that numbers are always more credible than other kinds of knowledge. When numbers are this big, this hurried, and come with this much at stake, it is important to step back and ask ourselves just what this number is saying and which kinds of thinking it is stopping. With the $700 billion bailout now law, we need to monitor the money like never before and focus on more permanent reforms that don't leave taxpayers holding the bag.

All investment depends on trust. But Americans aren't feeling so trusting these days. Even if we see the bailout as a collective investment in the financial markets that sustain a global economy, this feels less like trust than a giant leap of faith. It looks like we're all likely to be members of this 700 Club.

Wendy Espeland is an associate professor of sociology at Northwestern University.