The term universal exchangeability, which we have just used to describe one of the essentials of a medium of exchange, signifies that quality or combination of qualities which renders a commodity or a credit instrument universally acceptable to people in exchange for their goods or services. In a primitive community this quality or combination of qualities is the capacity to satisfy some fundamental want or wants, such as those for food or clothing or armour, but in a more highly developed state of society certain credit instruments quite incapable of serving as objects of general consumption possess universal exchangeability, and none of the commodities which constitute the medium of exchange enters into the consumption of every person, though all of them are extensively used for a variety of purposes and are highly esteemed by every one. It is, therefore, evident that other considerations besides the capacity to serve as an article of general consumption concur in the selection of the constituent elements of the modern medium of exchange. Among these, accuracy, convenience, and safety in commercial transactions are of prime importance.