A Comparative Study of the Extensive Role of Practical Reason in the Ethical Thought of Immanuel Kant and Mullā Ṣadrā

Introduction: Among Islamic moral thinkers—similar to Kantian ethical thought—the role of practical reason is highly prominent and is regarded as the sole gateway to true wisdom. This paper examines the extensive role of practical reason from the perspectives of Immanuel Kant—one of the most influential figures in the rationalist tradition of contemporary Western philosophy—and Mulla Sadra, the founder of Transcendent Philosophy (al-ḥikma al-mutaʿāliyah).
Findings: From Kant’s perspective, only the individual who adheres to the dictates of practical reason is genuinely free and possesses a form of life that transcends mere animal existence. Moral laws are universal, as they are grounded in the “transcendental self” and thus constitute a single, common reality for all human beings. Kant also grounds all theological proofs in practical reason and maintains that transcendence beyond the realm of sensible experience is possible only within the domain of practical reason.
questions:
l First, does practical reason contain a determinate list of moral rules?
l If the grounds of moral obligation are supplied by practical reason, are the justification, truth, and validity of moral decisions genuinely guaranteed? For example, patience is considered good because it is an effective means for achieving goals, but is it also morally true and justified?
l Is mere harmony and conformity with the structure of practical reason, by itself, sufficient to count as a moral reason or argument?
l Does conformity with the structure of practical reason adequately secure the universality and exceptionlessness of moral obligations, as Kant intends?
l Do the diverse manifestations of practical reason across different cultures undermine the stability of moral judgments?
In contrast to Kant, Mulla Sadra holds that ultimate transcendence beyond sensible experience and the attainment of true happiness depend on the theoretical intellect’s access to the knowledge of higher metaphysical realities. However, as long as the soul remains entangled in lower-level perceptions and needs, the theoretical intellect cannot ascend to the realm of higher intelligibles. Practical reason, through voluntary development and the free governance of the soul’s faculties, removes these impediments and enables the theoretical intellect to pursue truth.
With the flourishing of practical reason, human beings attain moral good, and this achievement represents a significant manifestation of voluntary substantial perfection. In Mulla Sadra’s philosophy, practical reason possesses a cognitive dimension and is strengthened through disciplined engagement in discerning real moral goods and evils.
points:
l The cognitive dimension of practical reason guarantees moral justification, truth, and validity.
l Harmony with the cognitive aspect of practical reason ensures the universality and exceptionlessness of moral rules.
l The cognitive dimension of practical reason is capable of generating moral reasons and arguments.
l Moreover, the cognitive and perceptual orientation of practical reason manifests a unified character across different cultures.
Discussion: One of the most significant points of divergence between the two views concerns the function of practical reason. In Kant’s dual-aspect framework, practical reason belongs to the inner, noumenal, or supra-phenomenal realm rather than the external, phenomenal realm. While causal necessity governs the phenomenal world, the noumenal realm is governed by the rules of pure reason. By contrast, in Mulla Sadra’s unitive metaphysical framework, practical reason, in one respect, is merely the soul’s motivational faculty responsible for regulating its powers, and in another respect, it is a cognitive faculty tasked with discerning morally beautiful actions from morally reprehensible ones.