CHAPTER I -- Section 4

In this brief section Hicks points out that the process of working out marginal utility theory in terms of indifference curves achieves the remarkable accomplishment of arriving at the same results while leaving behind some of the original information.  Specifically, Marshall's theory assumed we know a consumer's utility surface.  The indifference maps of Pareto's theory contain less information.  They are somewhat analogous to contour lines on a map without any key that tells us how much change in elevation occurs between adjacent lines.  It turns out that this extra information was not necessary to explain market phenomena.  And Hicks argues that, "on the principle of Occam's razor, it is better to do without it."