> The only thing that maintains the value of any asset (or currency) is the collective belief in that asset or currency.
Hello jmyeet! Unfortunately, I believe this statement, as you have given it, is untrue.
I hear it often, as it is continually and frequently asserted by crypto enthusiasts (and I am not suggesting you are one of those).
-----
For assets, value is grounded in utility (whether to do some useful function, generate some feeling, etc).
Asset price, on the other hand, could be almost anything depending on supply/demand and may be affected by beliefs at times.
It's important to disambiguate price and value. I can buy a superb pair of shoes from a desperate seller for $1, but that doesn't make their 'value' $1 to me or other people. Value can be personal, it can also be societal i.e. averaged over many people.
Indeed if price and value were the same thing, there would be no buyers or sellers, because you would have little reason to go to the effort of swapping two things of identical value to you.
-----
For currency, specifically, national currency where you are living in that nation - the value (and relative price) of a unit of a currency is grounded in taxation enforced by, well... force, by the state.
Taxation generates continual demand for units of currency regardless of individual or collective beliefs.
And in trust in the currency, again, is enforced by... force, by the state. Which prevents unlimited supply (by random people), again, regardless of individual or collective beliefs.
Thus, both supply and demand for the units of currency are set by the state, and supply/demand is what it takes to generate a stable price and mandatory use.
I note you mention trust, and 'backed by...' and 'might'.
However, discussing currency in terms of only trust and not in terms of taxation, misses half the argument. Both halves are essential for the argument to make sense.
Absent a mandatory minimum demand, control of supply of currency (and trust in that control) is meaningless.
In computing terms, you can see taxation + limited supply as a technique to 'bootstrap' an initial price for a currency without needing any shared or individual beliefs at all. It also underwrites the price in the long term, again, without any need for beliefs.
None of this is to say that a currency can't have its price/value shifted around by collective beliefs once bootstrapping / underwriting is in place. Of course it can. But what maintains, inescapably, a certain minimum price (your own words: maintain, inescapable), is enforced taxation.
-----
Going back to the price of assets. Well, you can believe all you want about, say, oil, and your whole country may have a collective belief, or even the planet, but since there is X units of oil needed and Y units of oil in supply, the price will be set by ongoing auction as always, or you can freeze/be stuck in your garage/factory shutdown. Supply and demand. Beliefs can affect supply and demand, of course. But supply and demand are primary, beliefs are secondary and they sit alongside necessity and physical reality.
-----
(Finally - again without wishing to imply you are a crypto enthusiast - a lot of crypto enthusiasts seem to imagine that mathematics has a similar 'force' to states, 'there can only be X coins', ignoring that a) chain algorithms/limits can be changed by widespread consensus b) no one is forcing anyone to use the crypto at all i.e. no physically enforced taxation c) it's trivial to substitute a chain with a duplicate chain (again consensus), as e.g. dogecoin proved rather effectively. They also invariably neglect the issue of needing 'mandatory demand' via taxation. I would speculate this is because the essential need for tax in currency systems, completely undermines the ponzi's disguise as a currency.)
(I use the word 'ponzi' casually here; technically ponzis are zero-sum, whereas crypto is worse - negative-sum, especially for the environment).