A Philosophy Written in the Mountains
Leibniz's Discourse on Metaphysics
Not many seminal works of philosophy are the product of an unoccupied mind in the midst of a failed mining project, but that, it seems, was the story behind Leibniz’s Discourse on Metaphysics. At the beginning of January 1686, he travelled to the Harz mountains to continue his (ultimately ill-fated) project to improve the productivity of the mines there via wind machines and water pumps of his own invention. When the work stalled for a few days, Leibniz did what he did best: he thought. At the beginning of February 1686, he remarked to a friend that as he had nothing to do for a few days, he had “written a short discourse on metaphysics”, a remark from which the text subsequently derived its name since Leibniz left it untitled. That “short discourse”—never published in his lifetime—would later become one of his most important philosophical works, as it captures the moment when Leibniz’s philosophical system came together.
He identified the main topics of the Discourse as grace, the concurrence of God, miracles, the cause of sin, the origin of evil, the soul’s immortality, and ideas. This is rather misleading, however, since these topics occupy less than a third of the text. A more accurate thematic structure of the Discourse’s 37 sections would be: God and his choice of the best (§§1–7), substance (§§8–16), physics (§§17–22), and the relationship between God and minds (§§23–37). What follows is a primer on the main topics and lines of argument in the text.
Leibniz’s Philosophical Papers by Lloyd Strickland: Vol.1: Universal Language, Characteristic, Logic, Encyclopaedia, and General Science. – Vol.2: Metaphysics, Natural Philosophy, Ethics, and Jurisprudence. – Vol.3: Religion and Theology. Click the titles for more information!
Starting with God
Leibniz does not begin with doubt, or with the external world, or even with the self, but with God, defined as “an absolutely perfect being” who possesses the supreme degree of power and wisdom. From this, Leibniz claims, it follows that God always acts in the most perfect way, as no other way of acting is consistent with the nature of God. Consider the alternative position defended by Malebranche, that God could have made a more perfect world but chose not to do so. Leibniz rejects this outright: to act with less perfection than one is capable of, he argues, is to act imperfectly, and that cannot be attributed to a perfect being.
Since God always acts in the most perfect way, Leibniz infers that the world we inhabit is not merely good, but rather the best possible world. At first glance, the idea can seem hard to accept, not least because the world contains suffering, injustice, and countless imperfections. Leibniz is well aware of this. But for him, the best world is not the one that lacks all of these things, but rather the one that is the simplest in terms of its underlying principles and the richest in terms of the variety of things it contains. Such, he claims, is the world we live in.
What Is a Substance?
After discussing God and his choice of world, Leibniz turns to a more technical question: what are the fundamental constituents of reality? Seventeenth-century philosophers had very different answers to this. Descartes, for example, had argued that there are two kinds of created substance: mind and body. Bodies are defined by extension, in other words by having size, shape, and motion.
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Not satisfied with this, Leibniz instead looks to Aristotle’s characterization of substances as subjects that have properties, for example individual plants, animals, and human beings. But he goes further. For Leibniz, a true substance must have what he calls a complete concept. This means that everything that can ever be truly said about a thing is already contained within it. To illustrate, take a historical figure like Alexander the Great. According to Leibniz, all of Alexander’s actions—his victories, his conversations, even the smallest details of his life—are contained in the concept of “Alexander”. A substance, then, is not just a thing with properties, but something whose entire history is built into its very concept.
This way of thinking leads Leibniz to a surprising claim about causation. Strictly speaking, he says, substances do not act on one another at all. Instead, each one unfolds its own states according to its own concept. What might look like interaction between substances is really the result of divine coordination: God has so established things from the outset that all substances mutually correspond with one another in such a way that their states agree. This is what Leibniz later calls pre-established harmony, though in the Discourse the idea isn’t given a name.
Bodies and Something More
At this point, Leibniz considers the nature of bodies. If bodies were nothing but extension, as Descartes had claimed, then bodies would be nothing but size, shape, and motion, and as such they would lack two crucial features: unity and activity. After all, a purely extended thing can always be divided into smaller parts, so it is hard to see how it could count as a single, unified thing. And it is equally hard to see how a purely extended thing could act, as opposed to being acted upon.
To account for these features, Leibniz reintroduces a concept that many of his contemporaries had rejected: the substantial form. In scholastic philosophy, this is an internal principle that gives a thing its unity and its activity. Although in the Discourse Leibniz does not fully settle the question of whether bodies qualify as substances in the strict sense (he crosses out a number of passages that bear on this question), he is clear that extension alone is not enough, as Descartes had claimed.
Leibniz draws support for his reintroduction of substantial forms from physics. He does this by showing that what is conserved in the universe is not the quantity of motion, as Descartes had supposed, but force, which is closer to what we would now call energy. Far from being just a technical point, it has metaphysical implications. This is because force is something that cannot be derived from extension and its modifications, like size, shape, and motion; as such, there must be something more in bodies than extension alone. That “something more” is substantial form. At the same time, Leibniz insists that natural phenomena should still be explained mechanically, without invoking hidden forms to explain why a stone falls or a body moves.
Final Causes: Is There a Purpose?
Another issue Leibniz addresses is the ends or goals in nature. Some philosophers of his time, such as Descartes, had argued that we should explain everything in terms of efficient causes (what produces what) and ignore final causes (what things are for), on the grounds that the human mind could not hope to discern God’s intentions. Leibniz disagrees. While he accepts that we cannot fully grasp God’s purposes, he insists that we can still recognize signs of them: when we see something that is good or orderly, we can reasonably say that it was intended. Nature, on this view, is not just a system of causes, but also a system of ends.
Minds and Their Place in the World
In the final part of the Discourse, Leibniz focuses on minds, since they are not just parts of the world; they can understand it. For this reason, Leibniz says, minds stand in a special relation to God.
He even describes a kind of “city of God”: a community of minds governed by divine wisdom. In this community, minds are not merely passive members but active participants, because they are capable of striving toward what is good. In doing so, they participate, however imperfectly, in the rational order of the universe.
Why Write the Discourse?
Why did Leibniz write this text? It is not entirely clear. He never published it, and he left no explicit statement of its purpose. But the context gives us a clue. Leibniz wrote in French, not Latin, which suggests that he was addressing a specific audience: French-speaking philosophers influenced by Descartes and Malebranche. Throughout the Discourse, he engages with their ideas—sometimes directly, often indirectly—and notes their shortcomings. His aim was not to score philosophical points but to defend a vision of the world that he thought was more consistent with both reason and religious belief.
A Philosophy Born in Idleness
There is something fitting about the origin of the Discourse on Metaphysics. It was not the product of a grand project or a systematic plan, but was written in a moment of pause, when Leibniz had nothing else to do. And yet, in that moment, he brought together ideas that would shape his philosophy for the rest of his life. The result is a text that is both provisional and profound: a snapshot of a mind in the process of thinking through some of the deepest questions we can ask: What is the world made of? How does it work? And what place do we have within it? Leibniz does not resolve every difficulty. But in this brief text, he sets out a vision of the world as ordered, intelligible, and purposeful, that he would spend the rest of his life refining.
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