"If there is no observation, does it not exist?" — Considering the structure of the world through Berkeley and quantum mechanics

1. Introduction

We believe on a daily basis that "what is there, exists."

However, when you pursue the question, "Can it really be said to 'exist' when no one is looking at it?", the premises of reality begin to waver. The 18th-century philosopher George Berkeley challenged this question philosophically.

And it was 20th-century quantum mechanics that attempted to answer the same question from the side of science. In this article, we will examine the deep relationship between the "existence" of the world and "observation" while comparing Berkeley's idealism with the measurement problem in quantum mechanics.

2. Berkeley's proposition: "To be is to be perceived"

To summarize Berkeley's thought in one phrase, it comes down to the following Latin: Esse est percipi = To be is to be perceived. For example, suppose there is a tree standing in a forest.

If you are looking at it, it can be said that it "exists."

But what if no one is looking at that tree? At that moment, does it really exist? Berkeley argues as follows:

• The world we perceive is not "things" as substances, but ideas floating in the mind.

• "Matter" and the "objective world" are actually just collections of sensations perceived by the mind.

• Therefore, what is not perceived does not exist.

3. Berkeley's idealism: This world is "inside the mind"

Berkeley's position is called subjective idealism. Everything in reality that we think is "there" is actually composed of the following:

•
Vision: red, blue, big, small...•
Hearing: sound, no sound...•
Touch: hard, soft...These are all sensations that arise in our minds, not "matter itself." In other words, Berkeley's claim is that the "outside world" is actually

the inner world (= the content of the mind).

4. "The world when not looking" is seen by God

So, what happens to the world when you are not looking at it, or when others are not there? To this question, Berkeley introduces the existence of God.

"The reason the world does not disappear is because God is constantly perceiving the world."

By having an ultimate observer called God, the existence of the world is guaranteed even when we are not looking. For Berkeley, God's perception is the guarantee of the objective world.

5. Intersection with quantum mechanics: "The state is not determined until it is observed"

On the other hand, there is a strange phenomenon in modern scientific quantum mechanics as well.

• Particles such as electrons and photons are in multiple states simultaneously until observed ("superposition" state).

• At the moment of observation, the wave function collapses into a single state.

• In other words, "without observation, the state is undetermined" = reality is determined by observation.

This has a structure surprisingly similar to Berkeley's idea that "existence is determined by perception."

6. Berkeley vs. Quantum Mechanics: Similarities and Differences

| 項目           | バークリー（哲学）               | 量子力学（物理学）                     |
|----------------|----------------------------------|----------------------------------------|
| 基本命題       | 知覚されなければ存在しない       | 観測されるまで状態が決まらない         |
| 世界の正体     | 心の中の観念                     | 波動関数（確率的存在）                 |
| 観測者         | 人間の精神、神                   | 測定装置、実験者                       |
| 現実の確定因   | 神の恒常的知覚                   | 観測による波動関数の収縮               |

7. Conclusion: "Observation" is the power to determine the world

Both Berkeley's idealism and the measurement problem in quantum mechanics have a common question flowing at their roots.

"By seeing, the world comes to 'be.' So, what is that which is not seen?"

Berkeley answered this with the existence of God, and quantum mechanics responded with the theory of probability and observation.

You are looking at this text on your smartphone or PC right now. At that moment, "your world" certainly exists. However, when you close it, what happens to the world in places you don't know...

It may be that it only gains meaning once it is observed.

Afterword: How to "perceive" the world

What do we believe in as "existing"?

That question extends from philosophy to physics, and then returns to our own daily lives.

Instead of just "seeing" the world, re-questioning "the very act of seeing"—

That is the message that Berkeley throws to the modern age as well.

* Subjective Idealism

Subjective idealism is a philosophical position that the "observer's consciousness" or "mind" is necessary for the material world or the external world to exist.

This idealism was systematized by Berkeley.

According to Berkeley's argument, the "matter" of the real world that we perceive does not exist independently as a substance, but is based on the idea that it exists by being perceivedThe core of Berkeley's subjective idealism

• Perception as a condition for existence: According to Berkeley, there is no substance in the material world; everything is merely "ideas perceived by the senses."

In other words, "an object exists" is a phenomenon that only holds true when that object is perceived by someone.

• The role of God: Berkeley believed that "the reason things exist even when I am not perceiving them is because God is constantly perceiving the world."

Through God's constant perception, the material world continues to exist without disappearing.

Berkeley's subjective idealism has been strongly refuted in subsequent philosophical discussions.

In particular, the position that "it does not exist unless it is perceived" raised the question of whether the material world is truly "dependent" in that way.

From a modern perspective, I will explain the problems and critical viewpoints that Berkeley's theory faced.

Criticisms of Berkeley's subjective idealism

1. The existence of objective reality

Berkeley denied the very substance of the material world, claiming that everything is merely an "idea."

However, many philosophers believe that there is an objective reality in the material world that does not depend on human consciousness.

From this point of view, an argument arose that Berkeley's position is too dependent on human perception, and that actual material reality exists independently of consciousness.

For example, from the perspective of modern science, it is believed that even if physical phenomena are not observed, the material world still exists according to certain laws.

Phenomena such as universal gravitation and physical laws actually exist and exert influence even when humans are not observing them.

2. Problems regarding the role of God

Berkeley stated that for the material world to continue to exist, God's constant perception is necessary.

He believed that "even when things are not being perceived, they continue to exist because God is always perceiving them."

However, this way of thinking has the following problems:

• Because it assumes the existence of God, Berkeley's theory is strongly predicated on a religious perspective, and it is difficult to prove the existence of God.

• Also, if perception by God is necessary, it may contradict the position that the material world exists independently of human recognition.

3. The problem of relative perception

Berkeley argued that "it exists by being perceived," but this way of thinking also has the following problems:

• If different people perceive the same material world in different ways, what becomes of the criteria for judging that the matter "exists"?

• In a world that depends on individual perception, the substance and properties of matter are not fixed, and the same things are perceived in different ways based on different perspectives.

Thus, making the "existence" of matter dependent on individual consciousness leads to the problem of the relativity of perception.

4. Conflict with modern physics

In quantum mechanics and modern physics, there is a characteristic that matter and energy are not determined until they are observed, but the position that they do not exist without an observer is considered too extreme.

Physics shows that even if there is no observation, physical phenomena (e.g., particles and waves) exist according to certain laws.

The idealism stated by Berkeley is the position that the existence of matter depends on the observer's mind, which is largely incompatible with modern scientific perspectives.

The possibility that Berkeley's subjective idealism is incorrect

There are several strong criticisms of Berkeley's theory, but it is not entirely wrong.

Rather, his thought provides important suggestions regarding epistemology and the role of the mind.

In particular, his deep consideration of the question of how the material world is "perceived" generated meaningful discussions in later epistemology and phenomenology.

However, based on modern scientific understanding, the position that the material world does not depend on human consciousness and that external reality exists regardless of the observer is supported, so it can be said that Berkeley's argument is incomplete from a modern perspective.

Conclusion

Berkeley's subjective idealism came to be criticized in subsequent philosophical discussions.

In particular, the position that the substance of the material world "exists through perception" strongly conflicts with the perspectives of modern philosophy and science, which acknowledge the existence of objective reality.

Nevertheless, Berkeley's theory is not entirely meaningless, and his thought still has an important influence in that it provided a perspective to re-examine the relationship between consciousness and matter.

With his arguably radical claim that "to be is to be perceived," Berkeley posed the following fundamental questions to us:

• "Do we really know the material world?"
• "Does the world exist when it is not being watched?"
• "Are consciousness and the mind things that create the world?"

Even if his conclusion (=subjective idealism) was incorrect from a modern viewpoint, the questions and the scope of thought it generated influenced later thinkers such as Kant, the phenomenologists, and modern epistemology, ontology, and quantum philosophy.

In other words, it can be said that Berkeley was a philosopher who redefined the very arena of philosophy by cutting into the "relationship between existence and consciousness" from the ground up.

Relationship with Descartes

Descartes, through "methodological skepticism", doubted the material world and his own body, and finally arrived at the proposition, "I think, therefore I am (Cogito, ergo sum)."

Descartes' thought takes the position of dualistically separating mind and matter, while harboring doubts about the reality of the "material world" in order to show that consciousness and thought certainly exist.

Differences between Descartes and Berkeley:

• Descartes doubted "matter (the physical world)" and established mind (thought) as the certain existence.

However, he did not completely deny the reality of matter itself. He believed that the existence of matter was guaranteed by God.

• Berkeley denied the very existence of the substance of the material world, stating that everything is merely an idea in the mind.

The material world exists only through perceivers, including God, and the idea is that without consciousness, the material world does not exist.

In Descartes, matter and mind are separate, and matter is supported by God, but in Berkeley, since all existence is within the workings of the mind (spirit), matter is also considered part of the mind.

Relationship with Kant

Kant approached the understanding of the material world through distinctions such as "things-in-themselves" and "phenomena."

For Kant, the world that humans can perceive is a "phenomenon" composed of sensation and perception, and it was considered that our cognition cannot reach the "thing-in-itself."

Kant's and Berkeley's thoughts have similar aspects, but there are also major differences.

Differences between Kant and Berkeley:

• Berkeley believed that the material world exists through perception, and that things exist as long as they are perceived.

Since matter itself does not exist, everything is merely an idea in the mind.

• Kant distinguished between the thing-in-itself (noumenon) and the phenomenon (phenomenon), and believed that human cognitive ability can only access "phenomena."

The thing-in-itself is an existence beyond human cognition, and we cannot perceive it.

In Kant's worldview, matter takes a certain form through our cognition, but the thing itself exists outside of cognition.

Influence of subjective idealism on modern philosophy

Berkeley's idealism influenced many subsequent philosophers and thinkers.

In particular, it has been re-evaluated from various directions, including counterarguments from phenomenological and realist perspectives, as well as the measurement problem in quantum mechanics.

Berkeley's thought raises the question, "To what extent does the material world depend on our consciousness?" and has become an important starting point for pursuing fundamental problems in modern epistemology, realism, and the philosophy of consciousness.

Summary

• Berkeley's subjective idealism is the position that the material world depends on the mind or consciousness and does not exist unless it is perceived.

• The difference from Descartes is that while Descartes divided spirit and matter dualistically, Berkeley denied the material world itself, asserting that everything is an idea within the mind.

• The difference from Kant is that while Kant distinguished between the thing-in-itself and phenomena, Berkeley believed that matter exists only by being "perceived by the mind."

Berkeley's idealism has had a profound influence on later philosophy and science by re-examining the relationship between the material world and the mind, and by clarifying the deep connection between consciousness and reality.

Bonus

To put the relationship between the three simply:

Descartes (1596-1650)

The father of modern philosophy; he started the world from reason and spirit.

Berkeley (1685-1753)

A subjective idealist who argued that only spirit exists (leaning somewhat toward mysticism).

Kant (1724-1804)

He critically inherited both and organized them by stating, "We only know phenomena."

The commonality among the three is the "problem of existence and recognition."

| 哲学者   | 認識の出発点               | 存在に対する考え方 |
|----------|----------------------------|----------------------|
| デカルト | 「我思う、ゆえに我あり」   | 精神（理性）こそ確実な出発点。物質の存在は二次的。 |
| バークリー | 知覚されること＝存在       | 物質は存在しない。知覚＝存在。神の知覚が現実を支える。 |
| カント   | 現象としての経験           | 世界は「物自体」としては不可知。私たちは「認識された世界」しか知らない。 |

[Philosophical genealogy of existence and recognition]

— Descartes, Berkeley, Kant —

[デカルト（1596–1650）]
   └─◆ 近代哲学の祖
   └─● 出発点：「我思う、ゆえに我あり」
   └─● 精神（意識・理性）の存在は確実
   └─● 外界の物質は“思考”によってのみ把握される
        ↓
[バークリー（1685–1753）]
   └─◆ 主観的観念論の提唱者
   └─● 出発点：「存在するとは、知覚されること（esse est percipi）」
   └─● 物質は存在しない。存在とは観念である
   └─● 神の恒常的知覚が世界の継続性を保証する
        ↓（バークリーの「主観的すぎる観念論」に反発）
[カント（1724–1804）]
   └─◆ 批判哲学の創始者
   └─● 出発点：「我々は物自体を知り得ない」
   └─● 認識は感性（直観）と悟性（概念）によって構成される
   └─● 世界は「認識された現象」にすぎず、「物自体」は不可知

[Flow of thought: Conflict and succession]

デカルト：精神こそ確実 → 外界は疑わしいが、理性で把握できる
   ↓
バークリー：精神しか存在しない → 物質は幻影、知覚こそ実在
   ↓
カント：どちらも極端すぎる → 世界は現象としてしか認識できない
         → 「物自体」は存在するが人間には到達できない

Related articles

The photonization of consciousness: The "I am made of light" hypothesis

What is an observer?

Added on June 18, 2026

Since this article was written quite early on, reading it back now, the flow of arguments is rather rough.

Berkeley's idealism, the quantum mechanical measurement problem, Descartes, Kant, and criticisms of subjective idealism are all mixed into one article, and the order of the questions is not organized.

However, I believe the questions themselves are still important.

"Does the world exist by being seen?"

"Can we say that things not observed exist?"

"Is the world humans see the same as the world that physically exists?"

These questions also lead to the theories of consciousness and observation I wrote later, and even the "photonization of consciousness" hypothesis.

If I were to rewrite this article in the future, I think it would be best to structure it as follows.

New title proposal

Does the world exist by being seen?

Subtitle
Thinking about the world before observation through Berkeley, quantum mechanics, and Kant

Proposed chapter structure

Introduction
How does the unseen world exist?

Chapter 1
Descartes: Is the only certain thing "I who think"?

Chapter 2
Berkeley: To exist is to be perceived

Chapter 3
God as an observer: Why does the world continue without disappearing?

Chapter 4
Quantum mechanics: Is the state not determined until it is observed?

Chapter 5
Philosophical perception and physical observation are not the same

Chapter 6
Kant: We live in "phenomena," not the "thing-in-itself"

Chapter 7
The unseen world and the world that does not become meaning

Chapter 8
Physical laws are a shareable foundation, and meaning arises within the individual

Final chapter
The world exists. But we can only live in the illuminated world

If I were to revise it, it would be important not to equate Berkeley and quantum mechanics too easily.

Berkeley's "perception" is a philosophical concept related to the human mind or God's recognition.

On the other hand, "observation" in quantum mechanics is a physical concept that does not mean only human consciousness, but includes interactions with measuring devices and the environment.

Therefore, they are not saying the same thing.

However, both pose the same kind of question to us.

How can we speak of things that have not been observed?

I think this question is the true core of this article.

I can rephrase it like this now.

The world might exist even if I am not looking at it.

However, the world for me only arises as something I have perceived, given meaning to, remembered, and illuminated.

In other words, existence and meaning are not the same.

Physically existing and having meaning within my world are different.

Organizing this difference would be the focus when rewriting this article.

In that sense, although this article is incomplete, it was an entrance to later thinking.

Berkeley said, "To exist is to be perceived."

I want to say it a little differently now.

Existence might be there even without being perceived.

But meaning does not arise unless it is illuminated.

And humans live in a world illuminated as meaning, not in existence itself.