Abstract. The question of the external validity of experiments has become a central methodological issue. It now dominates the question of internal validity, which used to be the crucial question and has been a guide in the construction of experimental economics as a well-established sub-discipline of economics. Is the requirement of external validity now the guiding theme in the evolution of economics? If the answer is yes, what will be the resultant changes in the discipline?
Mainstream economics as it emerged after the second world-war was thought of as a separate and complete science (Haussman 2008), putting on the side what are considered to be parasitic effects such as exogenous shocks. However, even in the very favorable sterile environment of the laboratory, observations do not fit the theoretical predictions. As this became apparent, the external validity requirement emerged as a defensive answer. Laboratory experiments, it is said, are unrealistic and are not therefore applicable to the real world. But this answer is only admissible if the idea of economics as a complete science is given up. This said, it is difficult to know what will be the result of this new requirement for experimental approaches, since we see contradictory objectives. Is the objective to expandthe domain of economics? Or to make the domain more precise? Or again, to make reality conform to the domain?
(Joint work with Yves de Curraize, LIPHA (Laboratoire interdisciplinaire d’étude du Politique – Hanna Arendt