Schumpeter regarded “The Nature of Capital and Income” as one of the three of Fisher’s contributions to general theory generally recognized, at the time Schumpeter was writing, as “of ﬁrst-class importance and originality.” The other two were Fisher’s “Mathematical Investigations” (1982) and his statistical method for measuring the marginal utility of income (1972). Nature is the bridge, both in sequence and in logic, between the other two great works, the timeless general equilibrium theory of the 1892 dissertation and the extension of that theory to intertemporal choices in production and consumption in the theory of interest.
Tobin, James, "Commentary on Irving Fisher" (1991). Cowles Foundation Discussion Papers. 1235.