Existential Deepening of Autonomy: A Comparative Analysis of Sartrean Authenticity and Kantian Deontological Ethics

Kant and Sartre are rarely examined together, particularly because Sartre is often portrayed as a thinker who defends an unconstrained and arbitrary conception of freedom. Such a reading, however, overlooks the normative dimensions of Sartrean thought and limits its dialogue with Kantian ethics. Employing comparative analysis, this study examines the normative convergence between Kantian autonomy, understood as the rational ideal of self-legislation in accordance with a universal moral law, and Sartrean authenticity, understood as the existential exercise of freedom against self-deception. The central argument is that Sartrean authenticity can be interpreted as an existential deepening of Kantian autonomy: while both positions reject forms of heteronomous determination and call for responsible self-relation, they articulate this demand within different registers. In both views, normative components can be identified concerning the exercise of freedom toward oneself and others. For Kant, autonomy requires the independence of the will from empirical determinations and heteronomy, together with rational self-legislation; for Sartre, authenticity requires the rejection of self-deception and the assumption of responsibility for one’s freedom. A parallel relation can also be traced between autonomy and respect in Kant, and between authenticity and generosity in Sartre. By examining freedom, responsibility, alienation, respect, and generosity, the study shows that Sartrean existential deepening extends responsibility beyond formal rational self-legislation into the domains of existential anxiety, situated choice, and the creation of values within concrete situations. Nevertheless, both perspectives connect freedom with human flourishing grounded in responsible self-determination. By addressing a gap in Iranian philosophical literature, where Kantian and Sartrean ethical paradigms have largely been treated as opposed, this study develops a conceptual framework for reconsidering the ethical significance of the intersection between rational and existential approaches. It thereby highlights a less-explored affinity between two radical philosophies of freedom and demonstrates Sartre’s capacity for ethical dialogue with contemporary debates.