The Leibniz Review

In the essay “Principia Calculi rationalis” Leibniz attempts to prove the theory of the syllogism within his own logic of concepts. This task would be quite easy if one made unrestricted use of the fundamental laws discovered by Leibniz, e.g., in the “General Inquiries” of 1686. In the essays of August 1690, Leibniz had developed some similar proofs which, however, he considered as unsatisfactory because they presupposed the unproven law of contraposition: “If concept A contains concept B, then conversely Non-B contains Non-A”. The proof in “Principia Calculi rationalis” appears to reach its goal without resorting to this law. However, it contains a subtle flaw which results from failing to postulate that the ingredient concepts have to be “possible”, i.e. self-consistent. Once this flaw is corrected, it turns out that the proof – though formally valid – would not have been approved by Leibniz because, again, it rests on an unproven principle even stronger than the law of contraposition.

The many equivocations that, in several respects, characterised the reception of Leibniz's Principes de la Nature et de la Grâce and Monadologie, up until the last century, find their origins in the genetic circumstances of their manuscripts, which gave rise to misinformation published in an anonymous review that appeared in the Leipzig Acta eruditorum in 1721. Archival research demonstrates that the author of this review, as well as of the Latin review of the Monadologie, which appeared, the same year, in the Supplementa of the Acta eruditorum, was Christian Wolff, who possessed a copy of the Leibnizian manuscrip since at least 1717. This translation figured as a precise cultural strategy that aimed to defuse any idealist interpretation of Leibniz’s monadology. An essential part of this strategy consists in reading the theory of pre-established harmony as a doctrine founded on a strictly dualistic substance metaphysics.