All is more or less proper to serve as a common measure, in proportion as it is more or less in general use, of a more similar quality, and more easy to be divided into aliquot parts. All is more or less applicable for the purpose of a general pledge of exchange, in proportion as it is less susceptible of decay or alteration in quantity or quality.
§ 39 - Reflections on the Formation and Distribution of Wealth (1766)