It's not really a "belief", it's backed by the real things you can do with it. For example, if your currency is accepted by any real estate agent, your currency

It's not really a "belief", it's backed by the real things you can do with it. For example, if your currency is accepted by any real estate agent, your currency has real value far beyond belief, since property has real value in our society. This is what cryptocurrency lacks, and why it's value is overstated.