Pretend that you know that civilization as we know it is going to end in your lifetime. Specifically, sooner than you'd like.
Is it easy or hard to do that sincerely? I'm not just asking you to fantasize about it happening to someone else, as though you were watching a disaster movie. Think about it happening to you. Think about it happening the way it would happen.
Civilizations end messily, chaotically, but not apocalyptically. That's still possible, owing to the proliferation of WMDs like nukes and bio-weapons. But that would likely be a symptom, as opposed to a cause. Nations or other political entities, like people, rarely engage in such consciously nihilistic behaviours unless they feel that they have little or nothing to lose.
Civilizations fall when they lose the strength to keep going.
OK, I'll admit: I'm not well versed in history. I know a few things, the kind of things generally well-educated people know. Nations go to war with one another. And wars usually put the last nails in the coffin. But the decline comes long before the war.
What happens, it seems to me, is that the people lose their will. To some extent, they lose direction, purpose, focus. They lose their cohesion, their identity. The become obsessed with entertainment, internal power struggles and political in-fighting. They become cynical, short-sighted, desperate, mean. They stop paying attention to the important things, the things that they depend on, the things that keep a country or society working. The fundamentals get lost by the wayside in favour of crackpot schemes, gaming the system, corruption and exploitation.
The bureaucracy becomes self-interested and self-serving. Politicians give up all pretence of serving their people. Businessmen depend more and more on pyramid schemes, scams, and taking advantage of the weak, the old, the ignorant and the desperate. The infrastructure is neglected. Social support systems are neglected. The long-term health of essential components of the economy are neglected: agriculture, manufacture of essential goods, foreign trade, essential energy supplies, other resources. Debt replaces work. Bankers and financiers abound. Fortune tellers and cults and false messiahs abound.
People turn inward. They lose interest in the world outside, in both the natural world and other societies. They ignore the warning signs. They are distracted.
A growing number of people, some alarmist, some measured, think these kinds of things are happening again, in the Western world, especially the United States but in all developed countries. Perhaps even the entire world.
The consequences of the neglect and self-absorption, the waste of time and energy on pointless competition, the exploitation in place of real effort, the blind conviction that everything we depend on will always be there, is that those things abruptly stop reliably being there.
Employment becomes unreliable. Government programs become unreliable. Roads and bridges become unreliable. Banks and insurance agents become unreliable. Prices vary radically as people become nervous and capital moves abruptly from one supposed safe haven to the next. Fear becomes more common. No one can agree on anything. People lose interest in what's actually going on in favour of choosing sides. Supply lines dry up. Food becomes scarce. Violence and civil disobedience increase in isolated places, at first, and then in other places, perhaps close to home.
When energy becomes suddenly expensive, or when essential raw materials for manufacturing suffer sudden bouts of scarcity, either due to speculation or hoarding or just plain shortages, chaos flares up. People call for order. They look to the first people who offer them that order, that forceful peace. They long for stability. But such things don't improve the scarcities or increase the availability of good health care or stop the increase in the unemployment rate or the murder rate. There are never enough police to ensure justice. Justice and other values, virtues, are either part of the whole social makeup, or they are absent. With the increase in desperation comes a decrease in virtuous behaviour as people seek to look after themselves at the expense of the weaker amongst them. People, at first metaphorically, but eventually literally, feed on one another.
That is when you know that we have returned to barbarism.