Taking Down Descartes: Leibniz’s ‘Dangerous Opinions in Descartes’ (1683 — 1685 (?)

There is a certain thrill in watching one genius try to demolish another, which is precisely what happens in the short but biting text, ‘Dangerous Opinions in Descartes’. Here, Leibniz doesn’t just disagree with Descartes; he treats Descartes’ Principles of Philosophy almost like a crime scene, flagging passages that he believes lead straight to atheism and fatalism.

Leibniz starts with Descartes’ famous claim that we shouldn’t try to guess God’s purposes. While this sounds humble, Leibniz immediately spots its dangers: if we can’t look at the ‘use of parts’ (in anatomy) or the beauty of nature and conclude that a wise mind designed them, then natural theology is dead. One of the most humanizing moments in this text is Leibniz’s visceral reaction to Descartes’ view of divine power. Descartes argued that God’s power over us is ‘absolute and totally free’, suggesting that he could treat us in any way he liked. Leibniz is horrified, arguing that this turns God into a ‘tyrant’ who is only ‘right’ because he can’t be punished. For Leibniz, God is bound by his own wisdom and justice. God doesn’t do things just because he can; he does them because they are the best.

The smoking gun for Leibniz is Descartes’ suggestion that matter successively assumes all the forms of which it is capable. In other words, if you wait long enough, everything that can happen will happen. For Leibniz, this smacks of Spinoza. If everything possible eventually exists, then there’s no room for a divine will that acts in the best way; instead, we’re just living in a cosmic machine that spits out every possible shape of matter, regardless of justice or beauty. Leibniz labels this ‘Nicodemite prudence’, essentially accusing Descartes of wearing a mask of Catholic piety while secretly harbouring a worldview not too distant from the one that Spinoza would later come up with.

This isn’t just petty seventeenth-century quibbling over details, but a fundamental debate about whether our universe is governed by reason (Leibniz) or blind necessity (the ‘secret’ Descartes). You can read Leibniz’s full, item-by-item takedown of Descartes—including his thoughts on the Eucharist and the ‘indefinite’ world—in the volume Metaphysics, Natural Philosophy, Ethics and Jurisprudence (part of the Leibniz’s Philosophical Papers 1677—1686 series), in which it appears in English for the first time.

— Lloyd Strickland, 9.iv.2026

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