Justice between the Ethics and the Politics: the Origin of the First Common Book of Aristotle’s Ethics

This article investigates the development of Aristotle’s theory of justice through a comparative analysis of Book v of the Nicomachean Ethics and key passages from the Politics. While the so-called “common books” (ne v–vii = ee iv–vi) have long been a subject of scholarly debate regarding their original attribution, recent studies by Dorothea Frede and Mi-Kyoung Lee suggest that first common book fits more naturally within the theoretical framework of the Nicomachean Ethics than the Eudemian Ethics. Building on their insights, this article seeks to clarify why Aristotle revised and expanded his account of justice in the form preserved in the Nicomachean Ethics. The analysis unfolds as follows: first, it shows that in the Politics justice is tied to the notion of the common good, serving as a criterion for evaluating political regimes; second, it explores how Aristotle grounds justice in law and equality within the Politics, while also noting unresolved tensions; third, it compares these findings with Book v of the Nicomachean Ethics, where Aristotle addresses these tensions by offering a more systematic rigorous account of justice as both lawfulness and equality. The article argues that this revision reflects Aristotle’s effort to integrate justice more thoroughly into his ethical theory and to respond to conceptual challenges that remained implicit in Politics.