Money originated before written history, with early concepts including Aristotel's "metallist" theory and Plato's "cartalist" theory. People traded goods directly, but unequal exchanges were common since goods lacked standard values. To solve this, money was invented as a standard unit of exchange. Gold and silver coins were the most common forms of money throughout history. Paper money was first developed in China during the Song Dynasty, originating from merchant receipts. Banking evolved from temples to distinct buildings under the Romans, though moneylenders still charged high interest rates. Banking was established in the British Empire by 1776 when Adam Smith's theories limited state involvement in banking.