Not sure what you're quoting, but what the quote seems to describe is known by other names, including "intersubjectivity", and is the very thing on which all our society and civilization stands. "Family", "loyalty", "society", "money", "market", "government", "law", "limited liability corporations", etc. are all abstract ideas made real through power of shared belief.

More specifically (and this is IMO critical), what pins such concepts down and makes them real, is not belief in the concept - but everyone's belief that everyone else believes in those concepts. E.g. it's not my belief in value of money that makes money valuable for me - it's my belief that the bank and the shopkeeper and the taxman all believe the money is worth something, which they do because they believe everyone else agrees too. This recursion allows us to expect certain things, such as me expecting to get food from store in exchange for money, and as long as enough people believe everyone else believes, the concept is as good as real.

Point being: this is not some gotcha or trickery, but the very stuff our lived reality is made off.