Leibniz's encounter with Spinoza's monism, October 1675 to February 1678

Mogens Laerke

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This article is concerned with Leibniz’s reading of Spinoza’s substance monism. It focuses on a particular period in Leibniz’s philosophical development, from October 1675 to February 1678. This period spans from the time Leibniz, in his De summa rerum papers, developed a rudimentary system in several aspects reminiscent of Spinozism, to the time he first read Spinoza’s Opera posthuma in early 1678. The article reconstructs a decisive shift in Leibniz’s attitude towards Spinoza’s substance monism that took place around 1677. Around 1675–1676, when Leibniz first heard of Spinoza’s philosophy from Tschirnhaus, Leibniz was playing with the option of a monist system where all things are conceived as modes of a single substance. He was also considering a parallelist metaphysical structure where explanatory parallelism between thought and extension is grounded in ontological parallelism. When Leibniz changed his intellectual setting in late 1676—moving from Paris to Hanover—his intellectual attitude toward Spinoza also changed, maybe in part as a result of his exchanges with the Danish catholic Nicolas Steno. In his critical comments on the first book of Ethics, from early 1678, Leibniz developed a comprehensive critique of Spinoza where he put to use and tested some of his own most recent philosophical discoveries. I thus show how he used his theory of predication to challenge Spinoza’s theory of attributes, and how he used the principle equipollence of the full cause and the entire effect to challenge Spinoza’s theory of causation and refute substance monism.
Original languageEnglish
Title of host publicationThe Oxford Handbook of Spinoza
EditorsMichael Della Rocca
PublisherOxford University Press
Number of pages50
ISBN (Print)9780195335828
Publication statusPublished - Oct 2017


  • Leibniz
  • Spinoza
  • substance monism
  • De summa rerum
  • theory of attributes
  • principle of equipollence
  • theory predication
  • Ehrenfried Walther von Tschirnhaus
  • Nicolas Steno
  • explanatory parallelism
  • ontological parallelism


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