The idea that price varies negatively with quantity demanded and positively with quantity supplied is a long-established one, although Hutchison (1953) has suggested that classical economists' ideas on supply and demand schedules were neither well defined nor consistent. Nevertheless, or perhaps because of this fuzziness, thr desire to make economics more scientific (both to express the theories more exactly and to provide a stronger empirically based knowledge) found expression particularly early in the field of demand. It was one of the first areas of economic theory to receive graphical and mathematical representation. This is generally believed to have been at the hands of Cournot in 1838, although his contributions to the development of economics were not appreciated until later in the century. The Victorian polymath Fleeming Jenkin developed the mathematical and geometric treatment of demand and supply further in a series of articles between 1868 and 1871. He even included variables to represent the other factors which cause the demand curve to shift back and forth. Although the use of mathematics was resisted at the time, it gradually became more acceptable since graphs and equations were good media in which to display the new ‘marginal’ theory.

The ‘marginal revolution’ of the 1870s is usually portrayed as changing the basis of the theory of value from the classical concentration on the production side to a new analysis based on the individual consumer. Blaug (1968) has described how this theory developed along two paths corresponding to the ideas of Marshall and Walras.