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Simple law of nature - everything could fail. Nothing is certain.
The common currencies are not 100% although there are 3 levels of backup for them.
The whole deal with human societies right now is a house of cards. It's all in our heads and does not really exist.
House of cards? Given structures are, yes. But the human has built in compulsive striving to build, to design and create, and to organize things. Many a huge city has been flattened in war, then rebuilt better within a decade.
This reality does exist. Any given structure is of course, temporal.