Money was historically an emergent market phenomenon that possessed intrinsic value as a commodity; nearly all contemporary money systems are based on unbacked fiat money without use value. Its value is consequently derived by social convention, having been declared by a government or regulatory entity 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", in the case of the United States dollar.
Legal tender is a form of money that courts of law are required to recognize as satisfactory payment for any monetary debt. Each jurisdiction determines what is legal tender, but essentially it is anything which when offered ("tendered") in payment of a debt extinguishes the debt. There is no obligation on the creditor to accept the tendered payment, but the act of tendering the payment in legal tender discharges the debt.
Some jurisdictions allow contract law to overrule the status of legal tender, allowing (for example) merchants to specify that they will not accept cash payments. Coins and banknotes are usually defined as legal tender in many countries, but personal cheques, credit cards, and similar non-cash methods of payment are usually not. Some jurisdictions may include a specific foreign currency as legal tender, at times as its exclusive legal tender or concurrently with its domestic currency. Some jurisdictions may forbid or restrict payment made by other than legal tender. In some jurisdictions legal tender can be refused as payment if no debt exists prior to the time of payment (where the obligation to pay may arise at the same time as the offer of payment). For example, vending machines and transport staff do not have to accept the largest denomination of banknote. Shopkeepers may reject large banknotes, which is covered by the legal concept known as invitation to treat. (Full article...)
Image 15Tibetan kong par tangka, dated 13-45 (= AD 1791),reverse (from Tibetan tangka)
Image 16Athens coin (c. 500/490-485 BC) discovered in Pushkalavati. This coin is the earliest known example of its type to be found so far east. (from Punch-marked coins)