In most modern economies fiat is backed by the 'full faith and credit' of the issuing government, which requires more young people paying into the pension system than retirees drawing from it. That's as clear an example of a Ponzi scheme as can be imagined, albeit moving on a slower timeframe than we usually think of such things working.

Fiat is backed by the insistence of the issuing government that you pay your taxes in that denomination. It has very little to do with pension systems, except to the extent that the government runs those also denominated in dollars.

But the US could end social security tomorrow and as long as it still required taxes and tariffs in the form of dollars, the dollar would still have value.

Zimbabwe required taxes and tariffs in the form of Zimbabwean dollars... You need a little more than just taxes and tariffs for a fiat currency to have value... You need a hard money that is not going to be devalued also. This is where all fiat falls short and has done since the demise of the gold standard.

Ok, but Zimbabwean dollar is not a Ponzi scheme either… the claim is about Ponzi scheme, not other things.

It's the best example of a fiat Ponzi scheme. Keep printing money to keep the guys near the printer (at the top of the pyramid) flush.

USD and other fiats are doing the same. Just at a much slower rate.

Edit:

It's basically just the Cantillion Effect[1] by another name.

[1] https://www.adamsmith.org/blog/the-cantillion-effect