Occidental Studies

Leibniz’s Critical Analysis of Cartesian Dualism with an Emphasis on the Theory of Pre-Established Harmony

Articles in Press

Document Type : Review

Author

Kamyar Pouraali

Ph.D. in Philosophy, Department of Philosophy, SRBIAU, Islamic Azad University, Tehran, Iran

10.30465/os.2026.53940.2090
Abstract
Introduction
The problem of the relation between “mind” and “body” in seventeenth-century philosophy was not merely an epistemological difficulty but culminated in a fundamental ontological crisis within the Cartesian framework. By sharply distinguishing between res cogitans (thinking substance) and res extensa (extended substance), and by reducing matter to mere extension, René Descartes depicted a world of two heterogeneous realms whose interaction remained problematic. His efforts in the Sixth Meditation, as well as in The Passions of the Soul (articles 31–32), to explain the union of mind and body through the pineal gland were, in Leibniz’s view, unable to overcome the categorical incompatibility between the non-spatial and the spatial. Even the potential appeal to “action at a distance”—a concept debated in the physics of the time—could not resolve the Cartesian impasse, as the lack of ontological proportion between a non-extended mind and an extended body rendered any transitive causal influence conceptually elusive.
Leibniz’s critique marks a radical transformation in the very meaning of “substance.” Challenging Cartesian geometric physics, Leibniz argues that “extension,” due to its infinite divisibility, lacks the genuine unity required for substantiality; for that which lacks simple unity cannot constitute a true substance (Leibniz 1996: 95–98). His alternative is the theory of monads: a pluralistic universe of simple, indivisible, and “windowless” unities, each being the active source of its own internal states (Leibniz 1996: 99–100). In this reconstruction, force rather than extension becomes the fundamental principle of reality, grounding both substantial unity and activity. Consequently, the mind–body problem is reformulated: it no longer concerns the interaction of two heterogeneous substances, but the correspondence between two internally coordinated series of states. Within this framework, “Pre-established Harmony” represents the culmination of Leibniz’s metaphysical reconstruction. Rejecting any physical influx, Leibniz maintains that the correspondence between mental and bodily states is not the result of causal interaction, but rather of a divinely preordained order established at creation, through which each substance unfolds its states according to its own internal principle while remaining perfectly coordinated with all others (Leibniz 2007: 23–24).
Drawing on primary texts, this article demonstrates how Leibniz’s substitution of “extension” with “force” reshapes the mind–body problem. The central question is to what extent Pre-established Harmony can resolve the paradoxes of interaction without reliance on perpetual miracles, and what new perspectives it opens for metaphysics.

Materials and Methods
This study adopts a descriptive-analytical approach, specifically utilizing the rational reconstruction of arguments. It proceeds along three main lines: First, the systems of Descartes and Leibniz are examined with a focus on substance and causality to identify key points of divergence. Second, Leibniz’s critique of Cartesian extension and his introduction of force are systematically reconstructed to present the theory of Pre-established Harmony in a coherent form. Third, these developments are situated within the seventeenth-century intellectual context, tracing their connection with Leibniz’s physical principles. The research draws directly on the original writings of Descartes and Leibniz, complemented by reliable commentaries, to clarify the ontological consequences of Leibniz’s transition from geometry to dynamics.

Discussion and Results
The analysis demonstrates that Leibniz’s critique of Descartes addresses the ontological foundations of substance and force. By replacing extension with force and introducing monads as indivisible centers of perception, Leibniz transforms the understanding of matter from a passive, inert mass into a well-founded phenomenon rooted in intrinsic activity. Pre-established Harmony resolves the causal impasse by substituting external interaction with internally coordinated, prearranged synchronicity. While this produces a law-governed system, it marks a shift from Cartesian geometric realism toward a dynamic ontology. Crucially, this is not a subjective idealism that denies the reality of the world, but rather an ontological framework where unity, force, and perception serve as the objective foundations of reality. The study concludes that Leibniz transcends the Cartesian framework by redefining the nature of substance itself, providing the conceptual groundwork for the subsequent development of modern metaphysics.

Conclusion
Leibniz’s philosophical project does not merely offer a reconciliation of Cartesian dualism; rather, it transcends the Cartesian impasse by fundamentally reinterpreting the nature of reality. By replacing the passive notion of extension with the dynamic concept of force, Leibniz shifts the metaphysical focus from inert matter to an active, pluralistic universe of monads. This reconstruction establishes a coherent system in which mind and body are harmonized through Pre-established Harmony—a model that maintains the integrity of each substance without the need for transitive causality.
The study concludes that Leibniz’s move from a mechanical universe to a structured network of self-subsistent unities provides a powerful metaphysical reformulation of the mind-body problem. By prioritizing the internal, law-governed activity of substances and their perceptual capacities, Leibniz’s metaphysics constitutes an important moment in the development of modern metaphysics. Ultimately, the theory of Pre-established Harmony represents a foundational shift toward a dynamic ontology that continues to resonate in contemporary debates regarding substance, causality, and the nature of consciousness.

Keywords

Leibniz
Descartes
Pre-Established Harmony
Monadology
Dualism
Descartes, R. (2008). Meditations on first philosophy: With selections from the Objections and Replies. ((M. Moriarty, Trans.) Oxford University Press.
Descartes, R. (2017). The Passions of the Soul. (J. Bannett, Trans.). Open Court Publishing Company.
Cottingham, J. (2005). The Cambridge Companion to Descartes. Cambridge University Press.
Leibniz, G. W., & Latta, R. (1948). The Monadology and other philosophical writings. Translated with Introduction and Notes by Robert Latta. (First). Geoffrey Cumberlege (Oxford University Press).
Leibniz, G. W., & Latta, R. (1996). The Monadology. Translated by Y. Mahdavi. Tehran: Kharazmi Publishing co. [in Persian]
Leibniz, G. W. (2005). Theodicy: essays on the goodness of God, the freedom of man and the origin of evil. Edited with Introduction by Austin Farrer; Translated by E.M. Huggard. Open Court Publishing Company.
Leibniz, G. W. (2007). The Discourse on Metaphysics. Translated by Jonathan Bennett.
Tabatabaei, M. T. (2021). “Descartes, metaphysical doubt and the foundation of method”. Gharbshenasiy-e Bonyadi (Fundamental Western Studies), 12(1), 167–189. [in Persian]
Occidental Studies

Articles in Press, Accepted Manuscript
Available Online from 12 March 2026

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