本論文認為,把憲法當作抽象理念的體現或具體政治鬥爭的結果,都將忽略其重要特質。因此,本論文補充了契約論的假設,提出制度論的觀點。制度論並不假設基於合意所訂的契約就必然會被執守,而強調訂約人為了追求更大的利益,永遠都有違約的可能。因此,憲法之所以具有正當性,並非其具有強制力,而是基於在共識決之下的「社會均衡」特質,亦即所有成員都無法單獨背離憲法而得利的狀態。同時,根據憲法所產生的秩序也必須是社會均衡。根據這些原則,本論文重新審視社會正義,證明羅爾斯所提的「無知之幕」乃制定公平憲法的特殊情境,但並非社會均衡的唯一樣態。據此,本論文也審視了實存憲法常見的困境與其補救設計,以及台灣憲政問題的根源。
This article argues that, to grasp the essence of a constitution, it is necessary to view it both as the embodiment of normative ideas and the outcome of political struggles. It shows this by constructing an institutional analysis, which rests on modified contractarian assumptions. An institutional theory does not presume that all parties signing a contract will automatically abide by it, and highlights the incentive to break the rules insofar a larger benefit is obtainable. Thus, the legitimacy of a constitution is not based on power, but on its social equilibrium nature. Originated in a unanimity rule, this equilibrium is a state where no one can defect to increase his welfare. Meanwhile, the constitutional order thus derived should also be a social equilibrium. On these principles, this article demonstrates that John Rawl's veil of ignorance is a special kind of social equilibrium out of which fairness can be claimed, but not a general state of constitution making. On the same basis, this article also examines the troubles faced by existing constitutions-in particular the one modified for six times in Taiwan in the past decade.