中文摘要：

本文提出最低正义准则，并证明唯一满足不相关选择的独立性、序数可比性和最低正义准则的社会福利函数是罗尔斯主义，唯一满足不相关选择的独立性、匿名性、比率不可比性和最低正义准则的社会福利函数是纳什社会福利函数。在常相对风险规避个体效用函数和纳什社会福利函数假设下，如果收入分配总是最优的，那么国民收入增长意味着每个人的收入都在增长，社会福利是国民收入的严格增函数，对称性最优所得税制意味着个体税后收入和社会福利都与起征点无关。

英文摘要：

This paper proposes the principle of minimal justice and shows that Rawlsianism is the only social welfare function satisfying independence of irrelevant alternatives, ordinal comparability, and minimal justice; Nash social welfare func- tion is the only social welfare function satisfying independence of irrelevant alternatives, anonymity, ratio-scale non-comparability, and minimal justice. Fur- thermore, under the assumption of constant-relative-risk-aversion utility ＇function and Nash social welfare function, if the income distribution is always optimal, then the increase of national income necessarily implies the increase of everyone＇s income, social welfare is strictly increasing in national income, and under optimal symmetrical taxation, tax-free threshold does not affect after-tax income and social welfare.