Well, you can try this if you like. Find another programmer, and you write code for him, and he writes code for you, and neither of you sell any services to third parties, and see how long that remains viable. There's "value" being created, you're both learning new stuff (for example).

But without someone to sell to, there's no money in this system, and therefore no way to get goods and services you need that can't be met within your microeconomy. So, not everyone can be a programmer, just as not everyone can be a bohemian.

I'm disputing your reasoning, not your conclusion. I fully agree that your conclusion is correct.

To survive, a person needs more than just wine and a B&B. That doesn't mean that a closed economy is a perpetual motion machine (and therefore can't exist), as the world economy proves.

It's also a good example why an isolationist foreign policy is a bad idea on a macro economic scale. A single country, no matter how big, simply cannot make all the stuff we take for granted in the modern world.