아마르티아 센의 파레토적 자유주의 불가능성에 대한 공공선택학파의 반론

Abstract

Kenneth’s Arrow Impossibility Theorem revealed dismal prospect to democracy, Amartya Sen’s Impossibility Theorem of Paretian Libertarianism provoked deep pessimism to Libertarianism. This paper synthesize critique by Public Choice School on Sen’s theorem comprising three points. Firstly, Sen misunderstood individuals as picking ‘social states’, which he regarded as complete description of society including all individual positions on it. Actually, however, individuals just choose particular aspect. Secondly, Sen’s impossibility basically comes from externality of individual’s preference. Public Choice scholars revealed, by designing proper game model under externality, Pareto optimality comes along with libertarian choice. Thirdly, Sen’s Impossibility Theorem is just short-term equilibrium showing contradiction between Pareto principle and Libertarian principle. Buchanan proves that paradox can be resolved through mutual coordination between individuals who are under Paretian inferior equilibrium. This paper suggests some implication as follows. Firstly, Libertarianism in Sen’s sense is far from normal meaning of liberty. Without proper conceptual modification, his theorem needs to be renamed. Secondly, If Sen’s Impossibility Theorem under U-condition can never exclude some cases in which two principles can coexist, then his theorem can be renamed as “Impossibility of Sen’s Impossibility of Paretian Libertarianism”. Thirdly, Public Choice theorists properly proved Paretian Libertarianism is possible, showing Sen exaggerated the paradox. Then, as Arrow’s theorem can be interpreted as ‘Possibility’ Theorem, considering substantial stability of actual collective choice situation, Sen’s theorem also can be re-interpreted as ‘Possibility’ Theorem of Paretian Libertarianism. Two camps needs to confront each other again towards the empirical proof on it.