Here's my rant for the day 
Currently we operate within a belief system, money.
It is a belief system as it's a shared understanding of how the world works, in the same way religions used to be.
Of course many people are still religious, but capitalism has replaced religion in many ways. It used to be that everyone in the West believed in the Christian god. It was unquestionable to not believe. People fought about their methods of worshipping the same god, but not about whether he was real. Everyone used to operate by the same moral code - whether they stuck by it or not, they knew the bible was a clear yardstick for morality, and it applied to everyone.
Now religion has become a personal preference, we have lost that particular shared moral code. In its place we have money and capitalism. We are so used to it, it is so much a part of our lives, that people are not in the habit of questioning it, in the same way the existence god was unquestionable, but still it governs how we live and relate to each other. It applies to all of us.
The actual pieces of paper - or computer code which makes the figures in our bank balance - have no actual real worth in reality. The banks stopped associating each piece of paper with an actual bit of gold a long long time ago. The whole system only works because we chose to believe in it. If we stopped believing in it, the system would collapse.
Along with the system of money come some powerful beliefs, such as that a person's labour is something which can be bought and sold. That "greed is good" and self-worth and the amount of money you have are linked, that mass accumulation of wealth by a small number of individuals is inevitable.
At the moment, people seem keen to stick to the money belief system we know and understand.
However empires come and go. The money belief system we have will eventually collapse.
In a system built on greed, not surprisingly, the rich are getting richer and more powerful and the poor are getting poorer The collapse of money may come about because those in power go too far, and the system becomes unbearable for enough people that we no longer want to assign value to money. (It is already pretty unbearable for millions, but not enough to tip the balance it would seem).
Or it may be that environmental disaster changes the primary concern for humanity to one of survival: the inability of a belief system based on short term greed to deal with a world-wide problem which threatens our very survival becomes so obvious that no one want to believe in money any more. Those who manage to survive the mass shifting of populations, extreme weather conditions, famine, floods (sound biblical? It could well be of biblical proportions!) may well not want to use the money-based system largely responsible for the problem, when picking themselves up after such devastation.
Or perhaps the system itself could collapse for economic reasons. It could be the root of its own demise. If the money system collapsed with little notice, it would cause great suffering as all our supply routes are based on money. How long would we survive here if imports largely stopped? It would be dire. I can't see people wanting to use money after that!
However it happens, the collapse of money ain't gonna be pretty. And Communism could start looking much more attractive then.
That's what I think anyway.
If you've managed to read all my ramblings, well done!
Off to do something world-saving now like .. umm .. playing trains with DS.