It had to come up. Every time metaphysical realism is taken seriously, the same objection arises, often with a knowing smile: "Yes, but quantum physics has shown that reality doesn't really exist like that..."

This sentence, despite its learned airs, is almost always false, and above all confused. It cheerfully mixes:

• an extraordinarily effective physical theory,
• problems of mathematical interpretation,
• and metaphysical conclusions that do not follow.

We must therefore be very clear from the start: quantum physics refutes neither realism, nor classical metaphysics, nor classical theism. It is certain philosophical interpretations of quantum physics that claim to do so—and they do it badly.

1. What quantum physics actually does (and what it does not)

Quantum physics is a formal theory:

• it models phenomena at a certain scale,
• it predicts experimental results with remarkable precision,
• it uses a specific mathematical formalism (wave functions, operators, Hilbert spaces).

But a physical theory never says what reality is as such. It says how certain aspects of reality behave under certain conditions and according to certain measurements.

Confusing a mathematical model with an ontology is already a category error.

No equation says: "reality does not exist." No experiment shows: "being depends on consciousness." These are philosophical over-interpretations, not scientific results.

2. The myth of the "observer creating reality"

One of the most widespread confusions comes from a naive reading of "observation" in quantum mechanics, often associated with Niels Bohr's school.

One then hears: "Before being observed, the particle doesn't really exist."

This is false.

In quantum formalism, a "measurement" is not an act of consciousness. It is an irreversible physical interaction between a system and a macroscopic apparatus. No brain is required.

When a detector clicks in a bubble chamber, reality does not consult the experimenter's opinion.

The error consists in illegitimately sliding from:

• the state of the system is described probabilistically before measurement

to:

• the system does not really exist before a mind looks at it.

This is an unjustified metaphysical leap.

3. Indetermination ≠ absence of being

Another classic sophism: confusing indetermination and non-being.

To say that a magnitude has no determined value before measurement does not mean that there is nothing. It means that:

• our classical description is inadequate,
• the system possesses a structure that is not reducible to simultaneous classical values.

But the indeterminate is not nothingness. It is a mode of determination that we do not fully master.

Down-to-earth example: An unborn child is neither an engineer nor a doctor. This does not mean it is nothing. It is determined otherwise, with real potencies.

The distinction between act and potency is here more pertinent than ever—and it precedes quantum physics by more than two millennia.

4. The false wave/particle contradiction

Quantum mechanics is often presented as a spectacular refutation of the principle of non-contradiction: an entity would be both wave and particle, which would be logically impossible. This reading is seductive, but it rests on a gross confusion between reality and our models.

The principle of non-contradiction forbids that a thing be and not be under the same respect, in the same sense, at the same moment. Yet quantum physics never affirms this.

It says something else, much more sober—and much more demanding:

The same physical system manifests different behaviors according to experimental conditions and interactions considered.

In other words, it is not an ontological contradiction, but an inadequacy of our classical categories.

Wave and particle are not essences, but models

The crux of the problem is here: we speak as if "wave" and "particle" designated fundamental ontological natures. Yet, historically and conceptually, they are phenomenological models, constructed to describe certain regimes of behavior.

• To behave like a particle means: localized interaction, point detection, discrete counting.
• To behave like a wave means: interferences, superposition, diffraction, extended propagation.

These descriptions do not say what the thing is in itself, but how it acts under certain conditions.

There is no contradiction in saying that the same reality:

• is detected punctually in a given apparatus,
• produces interference patterns in another.

The contradiction only appears if one absolutizes the models, giving them an ontological status they do not have.

5. Quantum chance is not a cause

"Quantum randomness" is often invoked as proof that reality would be fundamentally irrational.

Classic error.

Chance is never a cause. It designates either:

• ignorance of conditions,
• or a probabilistic description of a real process.

To say that an event is random is not to say it springs from nothing. It is to say that it is not univocally determined by accessible parameters.

A dice throw is random, but not absurd. Radioactive decay is probabilistic, but not ontologically incoherent.

Realism does not require strict determinism. It only requires that what is, be, and not spring from nothing.

6. Quantum decay "without cause"

One often hears the argument: "Radioactive decay occurs without cause. Therefore causality is false, or at least optional."

This argument rests on a massive equivocation on the word "cause." It confuses what physics can legitimately say within its methodological framework, and what metaphysics means by causality at the level of being.

Quantum decay is not without cause in the realist sense. It is without a determining measurable cause within the framework of the physical model.

This is not the same thing.

In quantum mechanics, one cannot predict when a given nucleus will decay. One can only assign a probability, a half-life, a statistical law over an ensemble.

This precisely means: there is no determining efficient cause, accessible and parametrizable, allowing prediction of the instant of decay.

But it in no way means:

• that the nucleus does not exist,
• that the decay springs from nothing,
• that there is no ontological reason for the event.

In the realist framework, the unstable nucleus:

• is in act as a nucleus,
• is in potency with respect to its decay,
• and this potency is real, grounded in what it is.

When decay occurs, there is no springing from nothing. There is actualization of a real potency, according to a non-deterministic mode.

Causality is not abolished. It is deeper than mechanism.

7. Quantum interpretations are not metaphysical discoveries

There are many interpretations of quantum mechanics: Copenhagen, many-worlds, Bohm, GRW, etc.

None is imposed by experiment. They are philosophically underdetermined.

In other words: the same experimental results are compatible with very different ontologies.

This should suffice to calm metaphysical enthusiasms.

When someone claims that "quantum physics has proven reality does not exist," they are not doing physics. They are doing implicit metaphysics, often poorly mastered.

8. Quantum physics presupposes the realism it does not explain

And here is the decisive point, always forgotten.

For quantum physics to be possible, one must already presuppose:

• that there is a real world,
• that this world is intelligible,
• that measurements are reliable,
• that mathematics describes something,
• that apparatuses exist,
• that results are not hallucinations.

In other words: quantum physics rests on the metaphysical realism that some claim to derive its negation from.

It does not explain being. It works within being.

Conclusion: quantum physics does not save the flight from reality

Quantum physics is not a threat to realism. It is a humiliation for simplistic metaphysics.

It shows that reality is richer, subtler, more demanding than our naive intuitions. It never shows that it is non-existent, absurd, or dependent on consciousness.

The temptation to shelter behind quantum physics to avoid the metaphysical consequences of reality is understandable. It is intellectually convenient. It is philosophically untenable.

Reality, even quantum, continues to be. And being does not let itself be dissolved in an equation.

Metaphysics, here again, does not disappear. It returns—as always—to demand an accounting.