New System of the Nature and Communication of Substances

The central argument is that substances are self-sufficient principles of action whose internal states unfold according to their own laws, and that the apparent communication between body and soul is a pre-established harmony orchestrated by God from the outset . Leibniz explicitly rejects occasionalism, the doctrine (associated with Malebranche) that God must intervene at every moment to coordinate body and soul, arguing that this would make God a 'perpetual miracle-worker' and violate the principle of sufficient reason . What the essay proposes instead is a naturalized explanation: God created substances with internal natures that correspond perfectly, so that their agreement follows from their own essences rather than from continuous divine intervention.

The New System appeared in the Journal des Savants in June and July 1695, a learned periodical read across Europe . Leibniz chose this venue deliberately: he was introducing a controversial metaphysical theory to a public audience and inviting debate. The essay was followed by a public exchange, most notably with Pierre Bayle, whose objections and Leibniz's replies were published in the same journal and in the Histoire des Ouvrages des Savants . This publication strategy reveals that Leibniz treated the New System as a provocation designed to elicit critical response, not as a finished doctrinal statement. The subsequent debate became an essential part of how the theory was developed and clarified.

The Discourse on Metaphysics (1686) was Leibniz's first mature system, but it remained unpublished in his lifetime. The New System (1695) is the public revision of that system, and the differences are significant. As one scholarly overview notes, by the early 1690s Leibniz's enthusiasm for the 'complete concept' theory of substance had waned, and his increasing preoccupation with dynamics led him to emphasize substance as an entelechy or spontaneous principle of action rather than as a logical notion . The New System reflects this shift: it presents substances as active forces with internal laws of development, not primarily as concepts containing all predicates. The essay is thus a transitional text, moving from the complete-concept framework of the 1680s toward the monadology of the later works.

Pierre Bayle was the most significant interlocutor of the New System. His Dictionnaire historique et critique and his journal publications raised sharp objections to the theory of pre-established harmony, particularly concerning the problem of how a soul could be said to act freely if its entire series of states is determined from the outset. Leibniz replied in a series of clarifications, published in 1696 and later, which became essential supplements to the original essay . The Woolhouse and Francks edition gathers all the key texts of this debate for the first time, noting that 'many appear in English for the first time' . The exchange with Bayle is not peripheral commentary; it is part of the theory's development, and reading the New System without it leaves the argument incomplete.

The most persistent misreading takes the denial of causal interaction to mean that monads are entirely isolated and that the apparent order of the world is an illusion. But Leibniz's point is more precise: substances do not interact through 'real or physical influence,' meaning immediate efficient causation, but they do interact 'ideally'—each substance expresses the entire universe from its own perspective, and God has arranged their expressions to correspond . The essay itself is careful to say that the action of one substance on another is 'neither an emission nor a transplantation of an entity, as the vulgar conceive it' . A related error treats pre-established harmony as a form of fatalism, when Leibniz insists that substances are active and spontaneous, their states flowing from their own natures rather than from external constraint.

The essay is included in the standard anthology Philosophical Essays, translated by Roger Ariew and Daniel Garber (Hackett, 1989), which is the most widely used scholarly edition . A dedicated edition by R. S. Woolhouse and Richard Francks, Leibniz's 'New System' and Associated Contemporary Texts (Oxford, 1997), gathers the essay together with the Bayle exchange and other related texts, providing the fullest representation of the debate . Leroy Loemker's Philosophical Papers and Letters (1969) also includes a translation. The Woolhouse/Francks edition is particularly valuable because it treats the New System as a public intervention whose meaning is inseparable from the responses it provoked, and it includes many texts translated into English for the first time.