The Temperature of the Brain: Edgeworth’s Thermodynamic Analogies of Utility Measurement

In 1881, Francis Ysidro Edgeworth attempted to provide a solid psychological basis for utility measurement. I will show that Edgeworth’s main struggle was to provide a possible measurement scale for a feeling—pleasure—using some kind of physical magnitude that would have allowed both intra and interpersonal comparisons, thus justifying the use of mathematical techniques to answer welfare issues. Edgeworth found inspiration in a similar quest, the invention of temperature, which had permitted the transformation of a feeling, “coldness,†into a physical quantity, temperature. Edgeworth faced two kinds of criticisms: concerning the use of psychological notions in economics and concerning the nature of utility itself. Both criticisms were also stated in terms of the thermodynamic metaphor, and the thermometer analogy played a major role in the exchanges. Following those criticisms and his own analysis, Edgeworth would move from a ratio to an ordinal understanding of utility, despite never abandoning the idea that economics should be psychologically grounded.