> To live in a world in which everything is provided for me, with no work and no effort, is to live in a world with no purpose.

Feeding and housing and clothing myself are not my "purpose", and many things which I find enjoyable would not be provided for me in an "age of abundance"; in fact, they are inherently things that no one else can provide for me.

I wish Yzupnick had left that part out, because the rest is true. Money falls out of a few simple assumptions, which just spewing them out in a simple HN comment (i.e. "please don't hammer me too much on the mathematical details") is something like: 1. For any given thing, different people have varying personal valuations of that thing. 2. As people have more of a thing, they value gaining yet more of that thing less per unit. 3. People can engage in the trade of goods.

From there it's a short step to bartering things for things I value highly with things I have too much of (or can make too much of) and therefore value less than my trading partner does, and from there only a slightly longer step before an economy develops in which there is a measure of fundamental market value, because the actors in the market conduct arbitrage until there are no more arbitrage opportunities, which mathematically implies the existence of a sort of standardized value measure.

I call money the most real abstract concept in the world. You can't actually have any of this "value", you can only have dollars or Euros or 1000 pounds of cabbage or something else real, but it underlies and informs every economic thing you do. You just barely can't touch it, it's just as real as it can be without quite being real. And money will exist until at least one of those three things is no longer true. (And even post-scarcity there will still be the little matter of time, and the trades thereof.)

(If this interested you, I really recommend at least the first few chapters of http://www.daviddfriedman.com/Academic/Price_Theory/PThy_ToC... .)

People value their time, but they don't value it like an economically-scarce commodity. For example, you may consider your significant other to have an "infinite line of credit" on your time, while you may actually spend more time actively avoiding people you don't want to spend time with, than the amount of time you'd end up spending with them (i.e. people can actually have a negative return on time—whereas the worst you can do with N dollars is to turn it into 0 dollars.) People are willing to give others as much of their time as they ask for, if they see some sort of benefit coming from it (e.g. monks living in a monastery their entire lives), while there is only a finite amount of money they'd be willing to spend in the same situation.

This is all because people do not rationally value their time vis. their finite lifespan, but unless you're expecting that to change somehow, you can just take that as a given.

Thus, since time is psychologically considered abundant, then assuming a world that is otherwise abundant, perhaps money would indeed be outmoded by something that captures the psychological value, rather than economic value, of time spent? I think Cory Doctorow's "whuffie" is a good start on that. Rather than whuffie changing as you give or take people's time (i.e. time-debt), it's actually a measure of willingness-to-lend-time, sort of like a credit score. If you borrow someone's bike and win a race with it, and they think that's cool, your time-credit-score goes up; if you wreck it or just disappear, and they don't like that, your time-credit-score goes down. The important bit here is that the credit score isn't actually tracking any sort of real debt, because, for the most part, people don't track time debt; they just write it off and re-evaluate how much time they'll be willing to lend you in the future.

"perhaps money would indeed be outmoded by something that captures the psychological value, rather than economic value, of time spent?"

That "something" would be a form of money. That was my point. If dollars were still around, there would be an exchange rate between dollars and whuffies, and as long as they could indeed be freely exchanged the eventual elimination of arbitrage opportunities (by virtue of exploiting them) would make them merely two more currencies. If dollars were not around but there were whuffies and huffies, both time-debt-backed currencies, there would be an exchange rate and the exploitation of arbitrage opportunities would make them look just like two currencies do today.

It does not take much for money to show up, and you would find that if such a new currency does arise and you insist that it's something new and "not moneyish" and you try to follow that up by your actions that you will be taken to the cleaners by people who know better. (In fact it's quite amusing to watch the desperate attempts by MMORPGs to avoid getting their currencies straight-up tied to dollars, and the only way to do that is to make every effort to ensure that there is no liquidity between the two currencies such that the balancing effects of the market can take effect, because otherwise they would end up freely convertible virtually overnight. I think the only reason they try to avoid this outcome so hard is the legal nightmare it would generate; the IRS is happy to tax anything that looks remotely like currency, by which I mean, this is not speculation, this is actual fact. You today can not dodge the IRS by making up your own currency.)

You basically said what I was coming here to say.

Money is any mechanism to store value that can easily and quickly be exchanged. Anything with sufficient durability and value per weight can be monetized if people choose to accept it in payment.