Leibniz’s most famous thought experiment begins with a machine. Imagine, he writes in 1714 in the Monadology, a machine so built that it could think, feel, and perceive. Now enlarge it to the proportions of a mill, so that one could walk through it. What would you find inside? Wheels, levers, gears — parts pushing against each other. Nowhere would you find perception (cf. Leibniz, 1714, Monadology, section 17).
This argument is over three hundred years old. It has lost none of its edge. Walk through a data centre today and you find silicon chips, copper traces, electromagnetic impulses. Nowhere do you find consciousness. Complexity has increased; the problem has remained the same: mechanism does not produce perception, no matter how many parts you assemble.
#Gottfried Wilhelm Leibniz and the Monad
Leibniz (1646-1716) was a mathematician, diplomat, jurist, and one of the last universal scholars of Europe. In the Monadology, a slim text of ninety paragraphs, he sketched an ontology that challenges the entire modern worldview. Against the materialist atomism that assembled the world from dead particles in empty space, Leibniz posited the monad: an indivisible, spiritual unity that forms the basic building block of reality.
Every monad possesses perception — an inner state that relates to the world. Not only humans have an interior; every being, down to the simplest, has a form of awareness. What contemporary physics treats as dead matter is, for Leibniz, an abstraction that dissolves the moment you sharpen your gaze. Dead matter is a surface effect, not a ground state.
What is decisive is what each monad does: it mirrors the entire cosmos from its perspective. Leibniz thought the relationship of part and whole not mechanically but as interpenetration. Every being contains the whole, sees it from its own standpoint — with varying clarity, varying consciousness, but never severed from it. Gwendolin Kirchhoff, in a conversation about Giordano Bruno and infinity, took up this thought: the human monad, human individuality in the deepest sense, is not the body but what actually ensouls the body, what makes it possible (cf. Kirchhoff, G., 2021, Das Unendliche und das Endliche).
#Pre-Established Harmony: Cosmos Without Mechanics
From the doctrine of monads follows a worldview that directly contradicts mechanism. If every monad is a self-contained unity receiving no causal influence from outside (Leibniz put it this way: monads have no windows), then the order of the cosmos cannot come about through external impacts and causal chains. Instead, Leibniz posited a pre-established harmony: an inner coordination of all monads that has existed from the beginning. The cosmos is not a clockwork that needs winding. It is attuned from within.
This idea is philosophically more significant than it first sounds. It says that coherence in the world need not be explained by external causes but can be thought of as a fundamental feature of reality. Jochen Kirchhoff described the deistic model, in which creation is set in motion once and then runs deterministically, as an impoverishment of this thought — because in Leibniz the divine will was still alive in the question of whether God was free and whether he could have created a different world (cf. Kirchhoff, J., 2019, Was wollte Nietzsche?).
#Leibniz Between Rationalism and Living Thought
The Monadology harbours a tension that is both fruitful and problematic for natural philosophy. On the one hand, Leibniz asserts universal interiority. Every being has perception, the cosmos is not a dead aggregate but a fabric of living unities. This places him close to Schelling, who half a century later formulated that nature should be the visible spirit.
On the other hand, Leibniz remains a rationalist. He constructs the whole deductively from logical principles. The monads are windowless, the harmony is pre-established, the best of all possible worlds is secured by the principle of sufficient reason. Jochen Kirchhoff placed this side of Leibniz alongside Berkeley and Kant: it is a trick to evade the infinite when you declare space and time to be mere forms of representation with no reality of their own (cf. Kirchhoff, J., 2021, Das Unendliche und das Endliche). Where Newton defended space as real, Leibniz held it absurd to think of space without objects. Both positions fall short of what natural philosophy demands: a space that is itself alive.
The reception history shows which side of Leibniz carried forward. His student Ruder Josip Boscovich pursued the anti-materialist impulses in the eighteenth century and rejected Newtonian atomism. Nietzsche discovered Boscovich in the 1870s and dismissively called the conventional atomic picture “lump-atoms” (cf. Kirchhoff, J., 1991, Anti-Geschichte der Physik). That Nietzsche rejected the mechanistic worldview owes to a line that begins with Leibniz.
#What Leibniz Means for Today’s Debate
The mill argument stands today at the centre of the debate about artificial intelligence. Anyone who claims that sufficiently complex computations generate consciousness must explain where in the mechanism perception appears. Leibniz anticipated the answer: nowhere. No enlargement of the machine, no increase in complexity changes this. Walk through the interior of a machine and you find parts in motion, not parts that feel.
For the natural philosophy in the tradition of Schelling and Kirchhoff, Leibniz’s significance lies in having defended interiority as a fundamental feature of being before materialism declared it settled. The Monadology thinks the cosmos as a fabric of beings, not as an accumulation of things. This does not reach as far as Schelling’s living natural philosophy, which understands mind not merely as distributed but as the organising force of the whole. And it does not reach as far as animism, which not only asserts interiority but experiences it as contactable and communicative. But it reaches far enough to mark a boundary that mechanism has not crossed to this day.
If you are concerned with the question of whether machines can think, it is worth starting with Leibniz — not because he gave the final answer, but because he asked the right question. Related: philosophy of consciousness (the hard problem and its history), epistemology (how humans know the world when they belong to it), panpsychism (the contemporary attempt to rescue interiority that falls behind Leibniz).