Any discussion on the psychology of money starts with the etymology of the word.
Money is anything that is generally accepted as payment for goods and services and repayment of debts. The main functions of money are distinguished as: a medium of exchange, a unit of account, a store of value, and occasionally, a standard of deferred payment.
Money originated as commodity money, but nearly all contemporary money systems are based on fiat money. Fiat money is without value as a physical commodity, and derives its value by being declared by a government to be legal tender; that is, it must be accepted as a form of payment within the boundaries of the country, for “all debts, public and private”. By law, the refusal of an offer to pay in legal tender extinguishes the debt in the same way acceptance does.
By this definition, one can surmise that money—initially “commodity money” and subsequently “fiat money”—represents the psychological glue that has always fueled commerce and basically facilitated and created civilization as we know it today.
Without a medium to enable commerce, there is no viable way to establish and maintain the complex network of relationships that comprise community.