Reader question: This – Was Iraq a fool's errand? – is a headline. What does "fool's errand" mean? Is it a set phrase?

My comments: An errand is a journey one takes in order to do something for someone. It's a usually a short trip for some light task. For example, your teacher may ask you to do an errand for him. He wants you to go back to his office and fetch some chalk for him. He'd forgotten to bring it with him to class.

That's probably a poor example but then forgetful teachers are nothing to be ashamed of. Teachers are human. All of them, I suppose, including the one who fled the classroom first during the earthquake in Sichuan last month, leaving his class behind.

Anyways, you get the picture of what an errand is.

A fool's errand?

That means it's a job only a fool will take.

Joking, but this lighthearted interpretation is more or less correct in essence. "A fool's errand" refers to a fruitless journey. If someone is sent on a fool's errand, it means they are dispatched to do a job for no good reason, or to accomplish a task at which they're not going to succeed.

In other words, it's an impossible mission – all the good work will be in vain.

"Was Iraq a fool's errand?"

From such a headline, we may safely infer that the author questions whether the war on Iraq would accomplish its goals, whatever those were. Probably not.

Is "fool's errand" a set phrase?

'Tis.

Here are media examples:

1. fool's errand

By calling for an end to the federal ban on offshore oil drilling, John McCain is placing a risky bet. He is wagering that skyrocketing gas prices have finally reached a tipping point, a threshold moment that has led voters to rethink their strong and long-held opinions against coastal oil exploration.

The stakes couldn't be higher: If he is wrong, McCain will have seriously damaged his chances in two key states with thousands of miles of coastline – California and Florida – and where opposition to offshore oil drilling has been unwavering. And he will have undermined some of his closest political allies in those states and others, including potential fall battlegrounds such as Virginia and North Carolina.

"Before $4.25-per-gallon gas, this would have been like pulling a pin on a grenade and rolling it into the state," said David Johnson, the former executive director of the Florida Republican Party. "It would have been a fool's errand to recommend it. It was never, ever a thing that a smart politician would have done in Florida."

- McCain plays with fire on offshore drilling, Politico.com, June 17, 2008.

2. on a fool's errand

New York City is a colossal urban beehive, and the perfect setting for a fascinating game about human behavior.

"Primetime" set up a seemingly impossible challenge for six pairs of people in different locations all over Manhattan: Try to find the other couples – all complete strangers – with no clues or additional information, just $100 to spend as they wished.

As daunting as the game appears, Yale economics professor Barry Nalebuff doesn't think the players are on a fool's errand. In his classes, he teaches game theory, which uses math to describe and even predict how people will behave in a whole range of situations.

"It [game theory] is the science of strategy. It's recognizing that the success of what you do depends on what other people do," Nalebuff said. John Nash, the mathematician featured in the movie "A Beautiful Mind," won the Nobel Prize for his work in game theory, proving there's a way for everyone in a group to be happy with the outcome.

Nalebuff says "Primetime's" challenge is an experiment in common perceptions. "Can I think about what you are thinking that I'll do? Can I put myself in your shoes as you are trying to put yourself in my shoes?"

- Mission Impossible: In Search of Strangers in New York City, abcnews.go.com, March 16, 2006.