LONG-BROWN-HAIR sat across from me, covering up her nervousness. She was a college student, a friend of a friend, fully half a decade younger than me. Our mutual friend had asked me to talk to her about careers — not recommending anything in particular, but reassuring her that one could indeed get a job with a humanities degree.

I thought about the Russian literature major who'd managed me at a tech company a decade ago. I considered the philosophy professor turned carpenter/activist who'd mentored me. And I told her a bit about my own degree in political science, and how much or little it had given me. No one cares about your degree two years after you graduate, I tried to tell her. It's about competence and skill sets and networking.

But I couldn't know that my sophomore year of college. I, too, probably wailed, "What am I going to do with a degree in poli-sci?" Most students at that age haven't yet enlarged their world views enough to see the big career picture.

Also, I couldn't know that I was being a zealot. Zealots never know they're being zealots. About English usage, about technology platforms, about superficiality.

It gets pretty gruesome, cataloguing all my childhood misapprehensions. Alcohol — the Teflon slope to ruin! Virtue consists of NOT doing certain delimited evil deeds! Real people have four-year college degrees!

But I grew up a bit and, more than that, I moved around. Moving kills off prejudices better than sheer aging does. And I'm getting better at recognizing blinders.

Residents of New York City hold a few assumptions that they rarely examine. Anything worth doing, you can do in Manhattan. Anyplace else in the U.S., other than maybe parts of California and New England, is insufferably provincial. There's nothing to do in cities under a million. Naivete is no defense in any conflict, and greed is moral, or at least not wrong.

This is not to say that the Bay Area doesn't have these sorts of blinders, too. There really are taboos and unchallenged assumptions in public discourse: the existence of guns is immoral, inequality of results necessarily proves inequality of opportunity and the perception of racism is as bad as racism itself.

It's so hard to work through my assumptions, to interrogate them and check them for weaknesses. I'm a cognitive miser — we all are — and we can't check that gravity exists before every step.

Then the other night I went to a class that made me even more pensive. I listened to presentations about why certain technologies had failed.

Betamax videotapes, the Iridium satellite cell phone system and the Denver airport automated baggage handler all shot for the moon and crashed hard. It wasn't just inexperienced sods like me who led these projects! Sony, Motorola, Steven Spielberg and other big names helmed them, all the while assuring themselves and investors of victory.

Most of the time, we saw in class, they just didn't check their assumptions. They didn't forecast their competition, their customers, the environment or the limits of the technologies. Billions of dollars went down the drain. I blundered along thinking that a political science degree was unemployable or that using Microsoft software was a death wish, but at least I only wasted six figures at most.

Do I have to mention the Iraq War?

Economics isn't the only area where blind spots get us. Sure, markets work best when buyers and sellers have the same information and resources to look for the best options. So our prejudices keep us from getting the best deals and might even contribute to power imbalances.

No one knows how the rules of the game might change tomorrow. But it goes even deeper than that.

If our assumptions blind us to what's really going on, how can we make sure we're acting ethically? One example: in sex, in psychology experiments, in drug use, we comfort ourselves with disclaimers about consenting adults.

It is impossible for a virgin to know what sex is like, and the same applies to new drugs or mindbending experiments.

How can you give informed consent to an experience you've never had before?

We are ignorant, not just of facts, but of the models, lenses and architectures we should use to evaluate the facts that we do have. All we can do is be glad when we're disoriented, because right after that comes a measure of enlightenment.

Sumana Harihareswara writes for Bay Area Living each week. Contact her at sumana@crummy.com.