One way that civilization might end is if somehow humanity is wiped out. Certainly this isn’t impossible, some might even say it is likely given the number of potential natural and man-made disasters that can do the trick. Philosophically, however, such an end is relatively uninteresting, with no more people there is nothing to say about their lack of civilization. Of course the possibility of human civilization ending might make nihilism seem unavoidable to some, may make the human enterprise seem pointless if it ends in such a sudden and terminal way. But I have addressed nihilism elsewhere, so I will say no more about it.
However, even without such a disaster and even if one dies civilization still might end. Civilization is a human construction and it exists because it serves a purpose. And so if it ever came to pass that we could replace civilization with something better, or were no longer in need of it, we would expect civilization as we know it to wither away. But before I can say how we might outgrow civilization or what life might be like without it I obviously need to make a claim about the purpose of civilization first. First let us distinguish civilization from an unorganized group of people. Before civilization existed there were still bands of people (although they probably had some primitive forms of organization). Still, we can conceive of bands of people without any structure, who tend to cohere because of the social needs of individuals. Civilization is something more than such bands, and thus its purpose is not social. As I see it then the purpose of civilization is to allow people to better satisfy their individual desires. By adopting an organizational structure people are able to accomplish more; labor can be divided and individuals can specialize. And thus society is able to produce more and to develop faster, and thus give people more of what they want.
So civilization becomes unnecessary only when people are able to satisfy their needs and desires just as well on their own as they can as part of an organized structure. This might seem to imply that civilization will always be needed. No matter what wonderful technologies we develop there will always be a need for raw materials, and since there are a limited amount of raw materials that we have easy access to there may very well be competition for them. And if technology can really satisfy all our needs it probably allows us to harm each other as well. Thus we might still end up with an endless struggle, and so we would still need civilization to maintain some kind of order.
The problem here is the inconvenient nature of the physical world. If we are physical beings then we will require physical things to satisfy our desires, and the physical world is finite, not to mention that the Earth is a relatively small place considering the number of people living on it. But being physical is terrible in many ways. As physical beings we have to obey physical laws. So we can’t travel faster than light, we can’t create matter and energy from nothing, and we can’t impose our will directly on the world. But in the long run we don’t have to live in the physical world, we could live in virtual worlds instead. And in a virtual world there are no such inconvenient laws, the rules are what we wish them to be. If we want to live in a world where we have to walk from place to place, eat and digest food to survive, and waste eight hours of every day sleeping we can. But we could also choose to live in a world where we could teleport at will, be immune to all harm, and never have to rest. In a virtual world all our desires can be satisfied instantaneously at no cost to anyone else, and so we have no need for civilization.
Admittedly that is a bit of an overstatement. Perhaps I should say that we only need an absolutely minimal civilization, because even if we all live in a virtual world someone would have to look after the physical machinery that runs the six billion worlds that we collectively inhabit. How we decide who has those responsibilities and how we ensure that they are doing their jobs requires some organization, but not much. Some might also think that the people living in these virtual worlds might compete for processing power, but such competition is really unnecessary. Everyone could be given an equal amount of processing power while retaining the illusion of an infinite amount of computational resources, simply by slowing down the speed at which they think when the computers need more time to process the task at hand.
What would life be like in such a post-civilization world? Obviously by the time people go digital we will have changed a great deal, and it is thus possible that people will be completely solitary without any need to interact. But I suspect people will still come into contact with each other, perhaps because they still have some need to be social, and perhaps because they will want to share their ideas with each other. The modern internet forecasts, to some extent, what such interactions will probably be like: relatively chaotic with only essentially self imposed restraints. Obviously the modern internet contains few “productive” interactions; because of the lack of structure it is hard to get anything done, there are no standards that elevate the most productive participants and suppress the rest (which is how things get done: by listening to the people who have proven themselves to be the most qualified and basically ignoring everyone else). But that isn’t a problem for our hypothetical future, because the people living in it have no need to be productive, a lack of productivity does them no disservice.