The problem is (IMO) some economists are much more confident that they should be given the degree of uncertainty in both their theories and data, and that in general a lot of economic theories are acted upon as though they are certain.

I think it's more of a case of people in power deciding what they want to do and then finding economists that agree with the policy to give it credibility.

And it's intriguing because in many cases, nothing about the unit in question changed between the day when everything was fine and the next day when the economy was in ruins. What changed was people's confidence.

An economy in ruins still exists, though -- the disappearance of a market (for tulips, comic books, or Enron stock) does not imply the disappearance of the larger system of supply/demand/exchange in which that market existed.

I disagree that this makes them ephemeral.

Fair point. Economies are real, and changes in them have very real effects. I think I would characterize them as ephemeral because it is possible for economies to not just collapse, but disappear entirely and need to be replaced by something else. Sometimes that's because of political calamity like war, or some natural disaster, but sometimes it's only because we stopped believing.

Something comes along to replace the economy in question, because the reality of our need to trade doesn't change, but we can disbelieve our ability to trade effectively out of existence for a time.

I think what Sean is trying to say is that economics is much more emo than government or law, and can trash its hotel room way faster. (Or, presumably, make a hotel room out of nothing way faster, although I think still slower than it can trash one.)

All abstractions can be metaphorized into rock stars, didn't you know that??

but sometimes it's only because we stopped believing.

Don't make me pull out Journey here, people!!

Trade you that Journey album for a bushel of wheat.

I think I like Nutty's description best.

And Jesse near killed me.

I don't see the implication that the effect of money or the economy isn't discoverable. It seems to me that you have an issue with the term semi-imaginary.

Right. Economies are not the same thing as things that are fictional, and I continue to find the idea that some parts of economics (i.e., currency) depend on certain shared beliefs (the value of currency) non-profound.

Jessica is right here:

But I don't know of any human society that does not exist on some level because people agree to trade things for other things -- economies develop because it is better to specialize and trade than to be self-sufficient.

The changing values of tulips, typewriters and AOL are interesting but not imagined; economies develop as Jessica notes and the valuing process is just a small part of it that doesn't impact the reality of economics as a part of society.

Journey is not worth a bushel of wheat. However, if you would like to take any (imaginary) Journey albums off my hands, I will graciously allow you to pay me in Beatles.

Ha. Beatles for Journey is like trading heavy dark Swiss chocolate for a picture of pooh.