“Eternal necessity” is a key concept in Islamic modal logic, and determining its nature and distinction from “absolute necessity” has long been a subject of debate among Avicennian logicians. This study, employing an analytical-historical method, examines the views of thinkers such as Avicenna, Fakhr al-Dīn al-Rāzī, al-Abharī, and others to explore the relationship between these two forms of necessity and the criteria of eternality.

The findings reveal that disagreements among logicians stem less from fundamental conflicts than from divergent interpretations of Avicenna’s expressions—particularly regarding the relationship between “perpetuity,” “necessity,” and “eternality.” This study identifies two major approaches within the Avicennian tradition: one that grounds eternality in the essence of the subject, and another that attributes it to the perpetuity of the subject-predicate relationship. This distinction serves as the core of the conceptual evolution of eternal necessity in Islamic logic.