The economy is an aspect of a society, just as economics basically has the same goals as sociology. Whenever two people interact, there is a type of economy.

Maybe it's just me, but it sounds like everyone is pretty much saying the same things and it's just a battle of semantics.

economics basically has the same goals as sociology

What are these goals?

Whenever two people interact, there is a type of economy.

So the null economy (defined by me as nothing being exchanged) still counts.

Interjecting for a list that will make your brain go kaflooey: Slate's The Explainer's Unanswered Questions

So the null economy (defined by me as nothing being exchanged) still counts.

If a tree is exchanged in the middle of a forest and nobody is around, does it still make an economy?

MWAH! Gud! I just wrote this entire post, which I deleted before hitting the post button, about how argumentation on the internet would be so much easier if only everyone took the whole medieval/aquinas approach where all of the terms are defined in advance.

I interupt Natter for a Christmas Miracle/Virgin Birth -- [link]

I think we are getting into the territory of people who bid $25 for $20 gift cards, on eBay.

These are people whom I would like to kick in the hindparts, or possibly rip them off.

I don't think I was explicitly asserting any of those things. I don't think changes in value, even drastic ones automatically cause an economy to disappear, but they do sometimes disappear. To the point of damaging the ability to trade effectively on many different levels. And I recognize that there are different levels of economic activity, in fact one of my points is that sometimes an entire level can be crippled or destroyed for a time. I don't believe I ever asserted that all economic activity can vanish with a thought, just that the amount of trust and consesnual reality involved in economic activity seems greater and to have a more significant impact than in other areas of human endeavor that involve high degrees of trust and/or consensual reality.

And I don't see where any of that implies that I think there cannot be scientific measurement, study or understanding of economics on any level.

You're contradicting yourself here in an important way, by saying that "even drastic ones automatically cause an economy to disappear, but they do sometimes disappear".... "I don't believe I ever asserted that all economic activity can vanish with a thought." And not only does this appear to be a contradiction, I don't know to what economy you're referring. Anyway, as to saying that economics/economies are similar to valuation in relying on unusually volatile and subjective concepts, this is what you said:

Probably the single most important thing to understand about economics is that it's all semi-imaginary. That is, economies only exist because we all agree to let them exsist, but economies all have very real consequences and effects. That's why even professional economists don't fully understand the economy. It should be completely under our control, and it is, except for the part where it's not.

And that's where you said that economics (the discipline) is semi-imaginary and that it can't therefore be fully understood, that economies wouldn't exist unless we all agreed to let them exist (which is demonstrably false, but I don't think you are holding that anymore, but in any case confuses the concept of valuation with economies), and implies that the argument that economies can wink out if we all disagree about value.

What are these goals?

What I think flea said upthread: to describe human behavior.

So the null economy (defined by me as nothing being exchanged) still counts.

Definitely, because people place value on other people's behavior, too. Even if our two strawmen did nothing but meditate, one would be willing to pay $X to make the other quit breathing through his mouth or wash his feet or whatever. The difference between an economist and a sociologist is that the economist would believe that the willing to pay number is the answer and the sociologist would draw in other factors before deciding the value of non-annoyance in this tiny little society of two.