Not Cadillac, CONDILLAC

Condillac  (1715 - 1780)

On this date in 1715 (or 1714 depending on your source), the french philosopher and economic liberal Étienne Bonnot, Abbé de Condillac was born. On the issue of property he was a Lockean and is credited by Guido Hulsmann with writing the first treatise on political economy based on subjective value. That treatise is Commerce and Government and appeared the same year as Adam Smith's Wealth of Nations. Regarding the importance of Condillac's influence on economics, Hulsmann has this to say in his biography of Mises:

The subjectivist theory of value survived only in this diffused form with one important exception: Etienne de Condillac’s great treatise, Commerce and Government. Published in the same year as Smith’s Wealth of Nations (1776), Condillac’s treatment gave the first full axiomatic presentation of political economy on the basis of the subjectivist theory of value. But the impact of his work was minimal because French economists rejected it. Condillac was already a famous philosopher when he published the book, and did not deem it necessary to follow the conventions of the disciples of Quesnay; rather, he presented his thoughts in an independent and original manner—an offense, it turns out, serious enough to prevent the translation of his work into English for more than two hundred years.

Still, Commerce and Government was one of the main sources of inspiration for Menger (who of course read French, among other languages) when he elaborated his economic value theory. Menger pointed out that value can only come into existence once human beings realize that economic goods exist and that each of them has a personal—or, as Menger would say “subjective” —importance. (Hulsmann, Mises, pp. 112-113). 

Hulsmann also notes that Menger quoted Condillac more than any other source besides Adam Smith and, whereas he was sometimes critical of Smith, his references to Condillac are always positive.