In early December 2025, I published a critique of the book Quantum History: A New Materialist Philosophy (Bloomsbury Academic, 2025), wherein I analyzed Žižek’s interpretation of quantum mechanics: A Critique of Žižek’s Quantum Ontology. Slavoj Žižek responded in early January 2026 with an extensive text titled A Footnote on the Quantum Incompleteness of Reality, in which he addressed my objections in depth and offered a systematic defense of his position.

This text is my reply to his response. The debate between us concerns one of the fundamental questions raised by quantum physics: what does quantum mechanics tell us about the nature of reality? Does the fact that quantum systems lack definite classical properties prior to measurement mean that reality itself is somehow unfinished or incomplete? Or is it simply that reality is different from how we are accustomed to thinking about it—not incomplete, but structured in a way that eludes our everyday notions?

What Does It Even Mean to Exist?

Before we delve into the debate of whether quantum reality is “incomplete” or “unfinished,” we must take a step back and ask a fundamental question: what does it even mean to exist? Without defining this concept, Žižek’s claim of an “ontological gap” has no clear meaning, as we do not know exactly what is supposed to be missing.

The history of science offers a good example of such predicaments. Mathematicians struggled for centuries with the paradoxes of infinity. Zeno’s paradoxes already hinted that a logical problem was hidden in the very heart of motion—how can one cross space if it is infinitely divisible? When Newton and Leibniz later developed infinitesimal calculus—a tool that was a necessary condition for the birth of modern physics and the precise description of motion—this predicament only deepened. They operated with quantities that were smaller than something, yet still not nothing.

This triggered a sharp response from George Berkeley, who famously labeled these elusive infinitesimals as “ghosts of departed quantities.” It seemed that a logical hole gaped at the very foundations of mathematics and that physics was building on shaky ground. But a turnaround came in the 19th century, when mathematicians strictly defined the concepts of limit, convergence, and continuity. Berkeley’s “ghosts” and Zeno’s paradoxes did not disappear because new facts about nature were discovered, but because the concepts they operated with were precisely defined.

I believe a similar conceptual clarification is needed in our debate as well. Therefore, I propose a working definition: a physical state exists if it is mathematically uniquely determined and causes empirical consequences. This definition entails two conditions. The first condition—mathematical determination—means that we can describe the state precisely, that it has a clear identity, that it is not ambiguous or undefined. The second condition—empirical consequences—means that the state is not merely a mathematical fiction, but leaves traces in the world that we can detect.

According to this definition, a qubit in superposition is a fully existing physical state. Mathematically, it is uniquely determined—if we know the wave function, we know everything there is to know about the system. The point on the Bloch sphere is precisely determined; it lacks nothing. And a qubit undoubtedly causes empirical consequences—interference, correlations, the operation of quantum algorithms.

Žižek’s claim that quantum reality is “incomplete,” therefore, presupposes a different definition of existence—a definition according to which something fully exists only when it possesses definite classical properties, such as position or spin along a given axis. But why should we accept such a definition? There is no reason to make classical properties the criterion for existence.

Two Interpretations

I can now summarize Žižek’s position and my own more precisely.

Žižek starts from the observation that quantum systems do not possess definite values of classical properties prior to measurement. An electron in superposition is neither “here” nor “there,” but in a state that cannot be described by any definite position. Only when we perform a measurement does the electron “acquire” a definite position. Standard quantum mechanics tells us which results are possible and what their probabilities are, but it does not tell us why we obtain precisely this result and not another.

Žižek interprets this to mean that prior to measurement, the electron lacks, for instance, a definite position because reality itself has not yet “created” it. Measurement is not the discovery of a pre-existing property, but the moment when reality is actually constituted. The world is thus not a closed whole with predetermined properties, but an open process that is constantly completing itself. In the very structure of being, there is a “gap”—a space of indeterminacy that is filled only through interaction.

My position is different. I agree that an electron in superposition does not possess definite properties in the classical sense. But I do not infer from this that it is “missing something” or that reality is not fully constituted. An electron in superposition is in a perfectly definite quantum state—only this state is not a state with definite classical properties. It is a state of a different type, described by the wave function. A qubit in superposition is not an “undetermined bit that does not yet know whether it is 0 or 1.” It is a perfectly definite state on the Bloch sphere, which is, however, neither 0 nor 1—it is something third, something unknown to classical physics.

Quantum Computers as a Touchstone

Philosophical debates on the interpretation of quantum mechanics have persisted for a century and appear irresolvable. However, in recent decades, something has emerged that can serve as a kind of empirical test: quantum computers.

A quantum computer is not merely a faster classical computer. It is a device that operates directly with quantum states and uses them as computational resources. When a quantum computer executes an algorithm, it exploits the fact that a qubit can carry more information than a classical bit, and that entangled qubits can show correlations that have no classical equivalent.

Here arises the key question for Žižek’s interpretation. If quantum states were truly “unfinished” or merely potential—if qubits floated in ontological indeterminacy that would be resolved only upon measurement—how could they serve as a reliable computational substrate? An algorithm requires precise control over states and predictable evolution. An entity that “does not know what it is” until we force it into a decision could not perform precise and reproducible calculations.

The fact that quantum computers work is empirical proof that quantum states are fully real entities with precisely determined properties. Superposition is not ontological indeterminacy, but a precisely defined state with which we can compute. Entanglement is not a “gap” in the structure of reality, but a source of correlations that we can exploit. Engineers building quantum computers do not operate with ontological gaps, but work with fully determined physical states that they must protect from environmental disturbances.

Quantum Error Correction: Can We Fix Something That Does Not Exist?

The argument regarding quantum computers can be taken even further. One of the most fascinating engineering disciplines of our time is quantum error correction (QEC)—and it is precisely this discipline that presents perhaps the toughest test for the thesis that quantum reality is “gappy” or “unfinished.”

In his book, Žižek uses the vivid metaphor of the universe as a video game, where a “lazy programmer” (nature) does not render the interior of a house until the player enters it, in order to save processing power. According to this logic, reality is optimized with emptiness; until we look at it, it is not fully determined. But if this were true, quantum computers could not function the way they do.

Quantum states are extremely fragile. Even the slightest disturbance from the environment—a thermal fluctuation or a random electromagnetic wave—can damage the information carried by a qubit. If qubits were merely an indeterminate “potentiality” waiting for our gaze to be realized, such damage could not be repaired. How can you fix something that is not yet truly formed?

Engineers have solved this predicament with a sophisticated process called syndrome measurement (or syndrome extraction). Instead of causing a collapse and erasing the superposition with a “full” question (“What state are you in?”), they ask the system only an indirect question: “Has an error occurred?” The system can diagnose its own injury—e.g., “the phase has flipped on the third qubit”—without revealing its content. Quantum information thus remains hidden and intact.

Based on this diagnosis, we can perform a precise correction—an operation that rotates the state back into the correct position. And here lies the crux of my argument: if the reality of the qubit were indeed an ontologically incomplete “fog” or indeterminacy, such surgical intervention would not be possible. You cannot break a gap, and you cannot fix a gap. You can only repair an entity that has a solid, existing structure. The success of quantum error correction proves that the information was there all along—fully present and real, even if inaccessible to our direct view.

Where Does the Collapse Come From? The Materiality of Information and the Transition Between Regimes

In his response, Žižek challenges me directly with a question: if quantum reality is completely consistent, where does the collapse of the wave function come from? What “forces” the waves to collapse? This is the central question of our debate and deserves a precise answer.

To answer it, I must first explain what information actually is and why its nature is key to understanding this problem. We live in a time when we often perceive information as something incorporeal, as if data were pure abstraction floating independently of the physical world. But this is an illusion. Every datum, every record, every memory requires a material carrier. Thoughts do not exist without neural connections and biochemical processes in the brain. A photograph does not exist without changes in the structure of the medium on which it is recorded. As physicist Rolf Landauer determined: information is inseparably linked to matter and energy.

Information can be understood as a physical state of a system that gives us an answer to a question. But here a key distinction arises. Some physical states can be read, copied, and transmitted without being destroyed. We can read a book and pass it on—the words on the paper remain. We can copy a file to another disk, and the original remains unchanged. This is the foundation of everything we call communication and knowledge transfer: the ability to separate information from its original carrier and transfer it without destroying it in the process.

However, when we enter the quantum world, this ability fails. Quantum states possess an unusual property: an arbitrary unknown quantum state cannot be copied without changing the original. This is not a technical limitation that might one day be overcome with better equipment. It is a mathematical consequence of the very structure of quantum theory, known as the no-cloning theorem. A qubit can exist in superposition, but if we want to “read” it—convert it into classical information that we can communicate—we inevitably change it.

Now I can answer Žižek’s question regarding the origin of the collapse. The key lies in the nature of the carriers of classical information. The paper we write on, the magnetic disk where we store data, the screen we read from—all these are macroscopic objects composed of an unimaginably large number of atoms and molecules. With such a large number of particles, the quantum nature of individual building blocks becomes irrelevant. Quantum effects are indeed still present at the level of individual atoms, but at the level of the entire system, they are no longer detectable or relevant. Macroscopic states are robust, stable, and—crucially—can be copied without destruction.

The collapse of the wave function is, therefore, not the consequence of some “gap” or deficiency in quantum reality. It is the consequence of the transition from a regime where we deal with individual quantum systems to a regime where we deal with macroscopic systems composed of a huge number of particles. In the first regime, quantum logic applies—states are rich but non-transferable. In the second regime, classical logic applies—states are in a sense impoverished, but can be copied and transmitted.

The randomness that appears during measurement stems from this transition. A quantum state is mathematically completely determined—a qubit pointing in a certain direction on the Bloch sphere has a precisely defined identity. But when we force it to express itself in the language of classical outcomes—“up” or “down”—this rich structure cannot survive intact. The result is determined probabilistically, and this probability is not a sign of a lack in reality, but a consequence of the structural difference between the two regimes.

Quantum computers vividly illustrate this difference between regimes. The main challenge in building them is not forcing qubits into existence—qubits exist quite really. The main challenge is keeping the system in the quantum regime long enough to perform the desired calculation. Engineers fight against decoherence—against the process in which a quantum system interacts with the macroscopic environment and transitions into the classical regime. The goal of quantum computing is to operate in the quantum regime as long as possible before we must translate the result into classical information that we can read and communicate.

Are the Parallels Between Quantum Physics and Language Relevant?

In his response, Žižek highlights structural similarities between the quantum world and the world of language: in both domains, possibility as such produces real effects; in both, an event becomes fully real only through some kind of registration; in both, we encounter specific temporal structures.

These parallels are interesting and worth considering. However, structural similarity is not the same as a deeper affinity. The fact that two systems exhibit similar patterns does not mean that they are driven by the same logic. Equations describing heat diffusion can also describe the spread of rumors in society, but this does not mean that society is driven by the same physical laws as gases, or that atoms “communicate” like people.

Even if these parallels held true in the full sense, it would not follow that quantum reality is incomplete in the way Žižek claims. It would follow, at most, that both systems are structured around a similar relationship between possibility and actuality. But this relationship is not in itself a relationship of lack.

And again, we can turn to quantum computers. If the connection between the quantum and the symbolic order were as deep as Žižek suggests, we would expect quantum computers to show a special affinity for linguistic or symbolic operations. But in reality, quantum algorithms are most powerful in completely non-linguistic problems—in integer factorization, in simulating molecules, in optimization problems.

Conclusion: Do Qubits Exist?

Our debate ultimately boils down to a single question: do qubits—quantum states in superposition—truly exist? Are they something actual, something real? Or are they merely some kind of intermediate, unfinished states waiting for a measurement to bring them into full existence?

The answer depends on how we define existence. If we take classical properties—definite position, definite velocity, definite spin value—as the criterion for existence, then qubits in superposition indeed do not “exist” in the full sense. They lack these properties.

This dilemma is not new. It recalls the famous debate of the late 19th century regarding the existence of atoms. Ernst Mach, one of the most influential physicists and philosophers of science of that time, insisted that atoms were merely “useful fictions”—mathematical tools for organizing data, but lacking real existence since they could not be directly seen. For Mach, only that which could be directly perceived existed; everything else was metaphysics. On the other side, Ludwig Boltzmann tragically insisted that atoms are real and that thermodynamic laws stem from their statistical motion. History sided with Boltzmann. When Einstein explained Brownian motion, it turned out that atoms were not merely computational shortcuts, but real building blocks of matter.

The parallel is telling. Mach rejected atoms because they did not fit his criteria of perceptibility, yet the development of physics went its own way. Are we not in a similar position today regarding qubits? Perhaps the success of quantum computers and the capability of quantum error correction remind us that the criterion of reality is not necessarily our direct experience or classical intuition, but the consistency and resilience of the structures with which we can interact in the world.

However, if we take mathematical determination and empirical consequences as the criterion for existence, then qubits undoubtedly exist. They are mathematically precisely determined—the wave function tells us everything there is to know about the system. And they cause empirical consequences—without them, there would be no interference, entanglement, or quantum algorithms. And perhaps most importantly: we can actively control, correct, and exploit these consequences, as demonstrated by quantum error correction.

Žižek’s perception of an “ontological gap” thus turns out to be the consequence of a specific definition of existence—one that perhaps held in the classical world but becomes too narrow when we enter the quantum one. Just as Zeno’s paradoxes dissipated when mathematics developed tools to describe continuity, the illusion of an “incomplete reality” dissipates when we abandon the requirement that a thing must have a classically defined form to count as real.

The quantum world is not unfinished. It is fully realized, only its structure is not classical. Quantum states are deterministic and cause measurable consequences, yet they exist in a regime that does not allow copying. The classical world, on the other hand, is based on robustness and reproducibility. The transition between them—what we call collapse—is not the moment when reality is just being “created,” but a transition between two modes of information organization.

Instead of a world full of ontological cracks, it makes more sense to speak of a world of two regimes. Our task is not the mystification of the transitions between them, but the understanding of the physical mechanisms that allow a stable classical reality, in which we can dwell and think, to emerge from a rich quantum foundation.

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Translated from the Slovene original, available here:

ANATOMIJA VEDNOSTI / Sašo Dolenc

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V začetku decembra 2025 sem objavil kritiko knjige Quantum History: A New Materialist Philosophy (Bloomsbury Academic, 2025), v kateri sem analiziral Žižkovo interpretacijo kvantne mehanike: Kritika Žižkove kvantne ontologije. Slavoj Žižek se je v začetku januarja 2026 odzval z obsežnim tekstom z naslovom…

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