二者関係における社会的動機の公理論的導出 : ―利他性と平等性の潜在性― An Axiomatic System of Social Motivations in Dyadic Relation: : Potential Existence of Altruism and Egalitarianism

　本稿の目的は，平等主義やマクシミン主義や競争主義など，他者配慮にかんする豊かな意味内容をもった二者関係における評価関数を，公理論的に導くことにある．この評価関数は，自他の利得差の絶対値を含むやや複雑な形をしているが，形式的かつ単純な仮定から導かれる．具体的にはこれらの仮定は，(1)自他の利得が比較できる，(2)利得と評価のそれぞれの（選好）順序が正アフィン変換によっても変わらない，というものである．これらの仮定は平等的な性質をもっていないようにみえるが，演繹的に導出される評価関数は平等主義的なものを含むのである．

     The purpose of this paper is to deduce axiomatically a bilateral evaluation function that has various meanings on caring about the other e.g. equalitarian, maximin, competition etc. The evaluation function of ones and the others payoffs looks like a little complicated including absolute value, but the function can be deduced from very simple axioms. Concretely speaking, the axioms are (1) comparable payoffs between actors and (2) positive affine transformation constancy on payoffs and evaluations respectively. These two axioms look like not including equality, but the evaluation function from the axioms includes equality. Because increasing affine transformation keeps the order property of payoffs. By the way the equality is defined as -|x-y| where x is ones payoff and y is the others payoff. Then the asymmetric property of absolute value of equality originates from the asymmetric property of the order of payoffs.