When a product is exchangeable on the market, it is a commodity. The private property spheres of entrepreneurs form the prerequisition for the existence of a commodity, because otherwise, the product exchanged is simply an economic good passing from one of its modifications to the next without the mediation of exchange. So if a product is exchanged for another product, everyone of the two is presented as commodity against the background of the other commodity on a market.
Historical Backdrop
• ARISTOTLE Economics: commodities have an equivalent value.
• JAMES MILL Elements of Political Economy: equivalent.
• FRANCIS EDGEWORTH Mathematical Psychics: indifference curve.
• JOHN COMMONS Institutional Economics: transaction.