I have used what will perhaps appear a somewhat clumsy phrase in place of the more familiar “Laws of Supply and Demand,” or even the “theory of the relation of demand and supply to value,” because I think it desirable to suggest that “Supply and Demand” are heads of arrangement rather than the name of a doctrine. When we say that the value of a thing depends on supply and demand, we do not, or at any rate ought not, to mean more than that we think it will be convenient to arrange the causes of changes in value under those two heads…. [From the text]