"In the medieval Mediterranean world, the intrinsic value of gold coin, the prevailing instrument of international exchange, remained stable for many centuries because any attempt to debase it would cause gold coins to flee elsewhere. In contrast, silver coins, the common currency, underwent steady debasement over time. Debasement, though decried by scholastic philosophers, was a practical necessity, since economic growth required a constantly expanding money supply. Given the limited supply and high production costs of precious metals, progressive debasement and depreciation of coin was the only alternative to ruinous deflation." "Fountain of Fortune", Richard von Glahn