Jacques Rueff (1896-1978) was a French economist who in the 1920s argued, in opposition to others, that physical sciences, such as thermodynamics, could be applied to economics. [1]

Education
Born in 1896, the son of a physician, Rueff was trained in science and mathematics at the Ecole Polytechnique. His attention was turned from the study of medicine when he studied classical economics under Clement Colson, and was especially influenced by the mathematical general-equilibrium theory of Leon Walras.

Overview of arguement
In the 20th century, it was argued by many that economics could never be an exact mathematical science. In contrast to this belief, Rueff devoted his first theoretical work, From the Physical to the Moral Sciences (1922), to methodology, showing that exactly the same scientific method can be applied to "moral" or "social" sciences like economics, as to the physical sciences.

The objection was typically raised that methods applied, say, to the theory of thermodynamics cannot be applied to the study of human beings endowed with free will. Rueff replied that just as there is no thermodynamics for a single molecule, there is no economics for an individual. The acts of individuals — individual particles in physics or free human beings in social sciences — are essentially "indeterminate"; yet in both cases, the pattern of behavior of a large number of individuals can be explained and predicted as a matter of statistical probability. The greater precision commonly observed in natural sciences is simply a function of sample size: while human beings in a national economy are typically counted in the millions (multiples of 10^6) or at most billions (multiples of 10^9), molecules are measured in moles (multiples of 6 x 10^23).

References
1. Mueller, John D. (2000). “Jacques Rueff: Political Economist for the 21st Century?” Ethics and Public Policy Center. January 28