It is a definition we find in Locke and, slightly earlier, in Vaughan; then in Melon 'gold and silver are, by general agreement, the pledge, the equivalent, or the common measure of all that which serves for men's use'; in Dutot 'wealth of credit or opinion is only representative, as are gold, silver, bronze, and copper'; in Fortbonnais 'the important point' in conventional wealth lies 'in the confidence of the owners of money and commodities that they can exchange them when they will. .