Between Illusion and Reality ……….. The world is no illusion

19 min readApr 15, 2025

1 Introduction

The word illusion is of Latin origin from the stem ludere or to play, i.e. to play with or mock something. In the course of the Middle Ages, it acquired its current meaning ‘deceptive hope, self-deception, pretence of something non-existent’. The word has a clearer meaning for magicians or ‘illusionists’ who deliberately and skillfully perform deceptions.

Definition: Scientifically (and philosophically) in the narrower sense, illusions are simply false interpretations of existing sensory impressions.

These illusions are false, but (mostly) normal, human reactions. They help to scientifically understand how our brain processes the signals of the sensory organs. Philosophically, this reinforces the importance of illusion as a concept: what is reality, what is not real? This is where the parable of the ancient philosopher Plato (428/427–348/347 BC) on illusion, the ‘Allegory of the Cave’, comes in. Perhaps only the Schrödinger cat is a similarly popular philosophical parable, although it was not created until 1935.

Fig. 1 Illusion in ancient philosophy:
The Allegory of the Cave by Plato. Image: Wikimedia Commons, 4edges (section)

In the parable, people live in a cave and see the shadows cast on the cave wall by moving figures — statues of people and animals and models of objects — as their reality (Fig. 1). The world as a whole is doubly illusory: in the first stage of the illusion, people see the moving shadows as reality; in the second stage, the shadow-casting figures are also artificial. Real life, the real sun and real people are outside, outside the cave. For Plato, outside the cave are the flawless ideal objects, the ideas — it is (presumably) the third stage of illusion. But there is also something real in the parable: the dolls and models are real — and their shadows.

2 What is not all “illusion”?

The world as a grand illusion.
Since Plato, the term illusion has been used for many things. The most comprehensive illusion is the idea that the entire normal world is an illusion. The definition of “illusion” is then philosophical and psychological

Definition: Illusion is an assumption that can be dissolved by another, “deeper” one and thus proves itself to be false.

The search for the “deeper” has a long philosophical (and religious) tradition. This is traditionally regarded as a sign of wisdom.

According to Plato,
the reason why there must be an ideal, better and purer world beyond or behind the “normal” world, is the unsatisfactory imperfection and impermanence of the “normal” world.

Fig. 2 illustrates the shortcomings of the real world with the bumpy hand drawing of a circle compared to the ideal circle demonstrated by the calculated image drawn by the computer. Plato was so fascinated by the precision of mathematics (mainly geometry) and the absoluteness of mathematical proofs “purely intellectual” that he transferred this contrast between the real (imperfect) and the ideal (perfect, pure) to the whole world. However, in the world, the real is dominant, only in mathematics is the ideal indeed behind approximations.

In the world, ideas grow from experience: in everyday life from experiencing the environment, in physics from learning from experiments. This is the viewpoint of Aristotle (384 BC — 322 BC), the student of Plato. He is thus the founder of natural science, even if many of his models were wrong — but the world is not an illusion.

The French philosopher René Descartes (1596–1650)
also discussed the world as a possible total illusion. The starting point of his thinking is that only he — the thinking ego — exists. The world is only a kind of dream. An evil demon, the Démon Maléfique, could make each of us believe it comprehensively. This point of view is poetic, but even for Descartes it is too extreme in view of the constraints of reality. It is a kind of spiritual total egoism or solipsism from the Latin sōlus ‘alone and ipse ‘self’. The zoologist and philosopher Rupert Riedl describes the grip of reality drastically:

“I am personally convinced that I could drive an entire solipsist congress into flight with an escaped wild rhinoceros.”

Descartes’ thoughts also do not stop at the solipsistic minimal form, the famous “I think, therefore I am” — cogito ergo sum, but he goes further. In his works, he recognizes different levels of reality. His systematic doubt ultimately gives rise to the scientific method.

The world as a simulation
Finally, there is a modern version of “the world is illusion”: the world as a simulation in a fictitious computer. The computer makes it possible to create quasi-natural views and forms. A particularly simple scenario is a fictitious brain-in-a-tank that receives its world signals from a computer (Fig. 3).

Fig. 3 Principle sketch of the
“brain in a tank” thought experiment. Image: Wikimedia Commons, Braininvat, Alexander Wivel.

The “I” in the brain communicates with the world via the computer, which imitates the outside world: the simulated movements, world views, physical experiments, fellow human beings and, in particular, the possession of one’s own body. The “I” lives fully in this simulated world. But it is not trivial to construct this illusory world.

If the simulation does not make a mistake in its code and execution, then the intermediate level of a simulation between us and the deeper level of reality would be impossible to prove. But in our experience with very large software systems, there would be errors that would be noticeable — up to and including a full system crash and restart.

The simulation program and the simulation computer would have to be gigantic:

1. A simulation requires much more effort in terms of instructions and hardware than the “real” program. The desktop computer in Fig. 3 is certainly not sufficient

2. The world simulation must not only answer human Quora questions, but also reconstruct the course of the laws of nature without contradictions. Or it would build such a contradiction-free system itself.

3. the simulation must not only recreate a human apartment, for example, but also the earth and the cosmos, at least in part.

Despite all the literature and films, such as the Matrix, the brain-in-a-tank is just an academic philosophical game. Similar to the concept of God, it is just pushing a problem “backwards”: Who created the creator? Here: What is behind the simulator, the true reality?

No, the world is not an illusion, but somehow a reality.

Instead of reproducing the world in a computer as a simulation, another computer concept is much more obvious and simpler: the world itself is a kind of computer, a processor of the laws of nature with a built-in random generator. It is the idea that the German inventor Konrad Zuse had around 1945 and published in 1967 (Zuse, 1967). It is curious how much philosophical interest the artificial idea “the world is an illusion” attracts in contrast to the realistic concept of the world as a processor that processes real physical laws.

3 Real tiny illusions and our personal model of the world

“Real illusion” seems to be a contradiction in terms, an oxymoron, but it is not. We are talking about illusions that occur as a matter of law because they are inherent in the normal cognitive process as intersections of different interpretations. The recognition distance (the Hamming distance) of the alternatives is too small and it is possible to slip into different interpretations. The interpretation of the brain simply slides down the wrong path.

Fig. 4 Rabbit and/or duck.
Historical tipping picture from a German magazine, 1892. Image: Wikimedia Commons,
rabbit and duck

This is particularly clear with images that can easily fall into two different interpretations. The simple image of “rabbit and duck” is particularly well-known in the history of philosophy. Depending on the direction of the glancing gaze, the recognition “it is a rabbit” or “it is a duck” predominates.

Hundreds of such illusions are known today, some of them marvelous, such as the pictures by the Dutch artist M.C. Escher or the illusions in the sky with the apparent size of the moon — large on the horizon, small high up — or the apparent misalignment of the crescent moon — not directly pointing to the sun. In addition, there are time effects such as the illusion of a sound that is forever rising or falling (a Shepard sound) or the movement of the rotating barber pole, which seems to be forever rising or falling.

Fig. 5 The Barbers Pole as an optical illusion. Image: Wikimedia Commons,
New York East Hampton Sag Harbor. Barber sign.

We build our little model of our world

In all these illusions, the brain takes the accessible information and interprets it with the help of previous knowledge. Even a small amount of additional information can trigger a new interpretation. The informational network that is triggered by a stimulus reflects the personal momentary experience, the quale (in the plural qualia). This creates a very personal, private model of the world that the brain uses to understand its place in the world, to understand what is going on around it and what possibilities for action exist. The personal world model must be as simple as possible in order to connect and explain the personal observations.

The conscious mind, perhaps also the subconscious, uses this model continuously or “streaming” for action. Qualia, world model and consciousness are all IT functions that are not available to the ego, but they are the ego. This small step from the outside into ourselves is difficult for many people to take. We are on the inside, we are the system!

When we bump into each other in the dark room, we improve our world model at this point (“caution — protrusive table leg!”, but there is no reason to declare the small world model as a whole an illusion. It is a legitimate approximation of our reality — the pain of bumping the table leg when the model fails proves it drastically. We live with a pragmatic, imprecise reality. The model is an approximation. Sensory errors are not a problem in principle; they are corrected by additional information. A particularly drastic example of a correction of historical importance for physiology, psychology and philosophy is the correction of the optical image in the eye.

Fig. 6 The real image inversion in the eye (brain) analogous to the camera obscura. Reality on the right, a real image of reality on the left — reversed. Image: Wikimedia Commons,
TheCameraObscura, Universal Magazine of Knowledge and Pleasure

The astronomer Johannes Kepler (1571–1630) discovered that the eye works in a similar way to the camera obscura known since antiquity (Fig. 6, Smith, 2022) It creates a small but inverted image of the outside world on the retina of the eye. Today we know that our brain inverts this image so that our movements in space conform to the movement in the inner image. Kepler is aware of the different types of reality that occur. There is the external view of nature, its image on the retina and the perceived image in the brain. The image on the retina is there as if painted (he calls it pictura), the image in the mind is the imago, only virtual. Nature is there when no one can see it, the pictura on the retina is there when the person is there, the imago is there when the person is actively looking at it. The imago disappears when the eye is closed, but this interpretation is not an illusion either. The pictura belongs to physics, the imago to information processing in today’s terms — but the difference was already clear to Kepler.

4 The big world model is not an illusion

Humanity as a whole is working on a model of the world. This task can be used to describe the overall task of the natural sciences: To understand all processes in the world and to collect all the facts.

A nearly closed example

A simple and de facto completed partial model is the surface and shape of the earth. Fig. 7 illustrates one of the most recently explored spots on earth, a table mountain in Venezuela. This table mountain inspired the writer Arthur Conan Doyle to write the novel The Lost World in 1912. Today, the earth’s surface is measured by satellites to the nearest meter or even centimeter, these images of the world are available on Google Maps and the streets of the world can be viewed in Google Streetview.

Fig. 7 Last gaps in the model of the Earth:
The Roraima-Tepui Table Mountain (1876)
Image: Wikimedia Commons, BritGY p149 — RORAIMA

The spatial shape of the earth is also known quite precisely. It is a pear shape with slight meter-sized undulations. The partial model of the world, our earth externally, is well recorded. There is no more room for poetic illusions of unknown worlds on the earth’s surface with remaining dinosaurs.

The physics part

The material, physical part of the world actually looks very down-to-earth and this-worldly, apart from the dissolvable illusions mentioned above. This is trivial because, after all, feeling and acting in the material world is our nature. According to Popper and Hehl, we call it the “first world” (Hehl, 2016). Yes, the stone is hard and real, and anyone who thinks it is an illusion will be struck by it. But modern physics has made the world less materialistic. This started in 1905, the annus mirabilis of Albert Einstein. There are two areas that are developing and make up modern physics: the theory of relativity, which describes space and time, especially on a large, cosmic scale, and quantum theory, which analyzes the innermost structure of the world. The statements of both areas are of the utmost precision, but the concepts undermine the everyday notions of space, time and matter.

Get Walter Hehl’s stories in your inbox

Join Medium for free to get updates from this writer.

Remember me for faster sign in

Since antiquity, time has been regarded as something intangible, an arbitrarily short present between the future, which does not yet exist, and the past, which is time that has already disappeared. But time is real and not an illusion. It drives all processes in the universe: the planets, the clouds, ourselves. Space is real, but it can be curved, in itself or with time as spacetime. Matter is very different from what was thought in the 19th century. There was indeed an illusion here for a decade or two: Atoms were thought to be tiny little planetary systems. It is also correct that atoms are essentially empty space. But there is no such visualization, even if there is some truth in them. There is no empty space either. The basic idea is that all kinds of matter and energy are actually “fields” with occasional knots. A physical field is space with special properties. The classic example is the magnetic field around a magnet or the electric field between two charges. Fig. 8 shows it schematically in the form of the field lines that simulate the path of test particles in the electric field of the two charges.

Fig. 8 The electric field around an electric dipole.
Image: Wikimedia Commons,
VFPt charges plus minus thumb, Geek3

So even fields are not illusions — the space of the field contains energy and momentum. Classical matter has dissolved, but the new foundations have not become an illusion, but a new, deeper reality.

The computer science section

But there is a second world of phenomena besides physics, which are immaterial by nature, the mental and spiritual processes and biological life. Are they illusions? An apt term from the 19th century was “world puzzles”, for example for the secret of consciousness or qualia. Some physicists were of the firm opinion that these phenomena could never be explained. One saying was Ignoramus et ignorabimus (Latin: We do not know and we will never know). What was missing was the entire technology for intellectual and spiritual things.

According to Hehl, this second world is everything that processes information and controls processes with information (Hehl, 2016, and Hehl, 2014). It is above all the clear and (philosophically) simple example of the computer. The question here is: Are programs real? Are computer programs “real” when they run? Or are we just talking about illusions?

Programs or software are information that executes actions and creates something new. Software companies are the most valuable companies of all in our time. Software controls large airplanes. There is no reason to think that software is an illusion. This also applies to running software that is currently being processed by the associated hardware. It is all real — at the latest it is painfully proven to be real when the software runs into an error. This corresponds to getting stuck on the table leg when the table becomes an indisputable physical reality.

Fig. 9 Computer program (symbolic image)
Image: Wikimedia Commons, Programming, Lorenzo Cafaro.

The category “software objects and information processing” also includes everything living and spiritual, in particular the processes of consciousness and qualia. Qualia are the ongoing processes of sensory perception, not seen from the outside but from the inside. As IT processes, they are naturally not an illusion.

The categorization of consciousness is more difficult. Consciousness is a distributed, flowing — i.e. continuously processing and acting — IT system. One difference to corresponding distributed digital systems, such as the software of a self-driving car, is the blurred nature of processing by neurological IT.

The big historical problem here is to imagine the process of conscious life — the felt consciousness — as IT:
Consciousness is simply the information processing going on as seen from the inside.
This results in our first-person shooter perspective. The processes are more or less standard IT. Our ego is in the middle of it, it is IT itself. This paradigm shift is difficult for many people; it seems incomprehensible to them that something supernatural and inexplicable is not needed to understand the ego. But the leap must be made; without it, the mind cannot be understood. Philosophy without this paradigm shift is like chemistry with phlogiston.

Although neurological information processing is almost immaterial and also blurred in the brain, blurring does not mean illusion: clouds are blurred, but bring real hail and rain. None of this is an illusion. Only when you see a hare in the shape of the cloud does this hare become an illusion.

Dreams are a particularly vague type of information processing, meaning dreams during sleep. The brain creates ad hoc scenarios from chunks of memory, wishes and fears, and probably with a lot of chance, which run alongside and within the machinery of consciousness. The laws of physics can be left aside. A dream is a fleeting piece of software, but a realistic phenomenon. However, being able to fly is an illusion — but it can still be a beautiful, liberating dream experience (Fig. 10).

Fig. 10 The Rocket Man as a dream example film 1952.
Image: Republic Pictures

Near-death experiences are a “particularly philosophical” variant of dreams. People who come back to life from situations of extreme physical distress report having experienced special phenomena, usually of a positive nature. Reports of the feeling of being outside the body and “watching and to see oneself” are particularly striking. The nature of the experience is influenced by the surrounding culture — in a Christian environment, for example, angels appear in the light, in India it is the god of death.

The system of running life, including consciousness and subconsciousness, is a tightly coupled system. It is natural for systematic and random disturbances to occur in extremely threatening situations and for special emergency mechanisms to kick in. The apparent stepping out of the body has become a meme. It is an illusion to understand this as a physical phenomenon; in physics, it is an illusion but the phenomena are a neurological reality.

Chance and illusion

A source of vagueness and a possible proximity to illusion brings the uncertainty of chance into the world. But there is chance, defined as an event whose cause is not accessible. This applies, for example, to the radioactive decay of a single atom or the collision of an atom or molecule from the myriad of moving molecules. It is an illusion to see a lottery win as a reward of fate — but the lottery win itself is simply a reality with the intricate rotations and impacts of the lottery balls.

5 The Ego (or the We), the models and the world

The models stand between us and the real world. Fig. 11 symbolizes our (my, your) knowledge and understanding of the world. The diagram should contain nodes and connections. It contains many things, from the arrangement of the furniture in the living room to the plants in my garden to the course of the highway to my place of work, from the intricacies of my own body to my knowledge of astronomy. It’s an ongoing battle for improvement on all fronts. I can live with some flaws in the model, even some inner conflicts (such as cognitive dissonance).

The personal world model is a pragmatic copy of the real world. It is the personal reality and not an illusion — and even more so the world, the blueprint for it, is not an illusion.

Fig. 11 The personal world model (symbolic image)

Humanity as a whole has developed a larger, even gigantic world model over many generations (Fig. 12). It is a super-network of various subsystems. There are also subsystems of varying quality connected to it, always with false doctrines or illusions such as pretended visits from aliens or legends of sunken countries.

Fig. 12 The world model of humanity (symbolic image)
Generations of people on the left, accumulated reality on the right.
In between the world model.

Not only for physicists, the core of the model is fundamental physics, as mentioned with relativity and quantum theory. A myriad of experiments have confirmed it, and, above all, mathematics holds it together. It is the incredible way in which mathematics and physics fit together that reinforces the explanatory power of the model of the world. At least the physical part of the world system is so closely connected and mutually interlocked that it is difficult to change the structure. Possible extensions of physics, such as those hoped for in quantum gravity, must continue to support the enormous amount of previous experience.

Both models, the personal model and that of the culture of mankind, are information, but not an illusion: the personal model allows us to live an everyday life, the large model of the world allows us to carry out complex experiments and often predict the result with high precision. The models are as close to reality as we can get. They are our reality. Evolution on the one hand and the development of science and technology on the other have ensured this. The approach does not deny that the real world actually exists: Reality is not an illusion either.

The systematic approach to reality through pragmatic models is already the basic idea of Stephen Hawking and Leonard Mlodinow in their 2010 book The Grand Design (Hawking, 2010). They call this interpretation of the world model-dependent realism. It is science that delves into the world as deeply as possible — but not further.

Fig. 13 Allegoria de la simulation,
Lorenzo Lippi, 1606–1665.
Wikimedia Commons, allégorie de la Simulation
(musée des beaux-arts, Angers).

This philosophical oil painting by the Baroque painter Lorenzo Lippi in Florence, painted around 1640 (Fig. 13), is an allegory for the modeling of the world. The mask in the young woman’s hand corresponds to the model of the world; it is a true-to-life depiction of the face. The living woman is real nature, evolving over time. In her left hand, the woman holds an open pomegranate with numerous black seeds — perhaps to be interpreted here as the multitude of ideas and concepts needed to describe the world.

6 Conclusions — Where are illusions?

Our models of the world, personally and as humanity, stand between illusion and reality. Statements that conform to the larger model are approximate reality and not an illusion. This includes some of the big ideas, such as: What is matter? What is life? What is consciousness? For mental processes, it is essential that programs and running programs are also real and not an illusion.

If someone uses an incorrect, perhaps outdated, model, such statements are easily illusions. A trivial example is the flat Earth model. It works quite well within a radius of a few kilometers, but becomes absurd at large dimensions, or even more so when the earth is viewed from space. This is actually a killer argument for flat-earthers in the age of space travel!

For many such pseudo-philosophical illusions, there are killer arguments that can be used to disillusion “illusions”:

“The world is an illusion” — stick to it if a rhinoceros comes in.
“Life is an illusion” — “whoever says that should give birth to a child.”
“Consciousness is an illusion” — no longer when you bump into the table leg again.
“Everything, even stones, has consciousness” — this is illusory. Consciousness requires a highly developed IT system. Stones (and crystals) can trigger deep emotions, but they cannot heal sickness.
“We humans are something completely different, much more than animals” — no longer applies when someone smacks their lips loudly while eating.
“Death is an illusion” — only a young, healthy person believes that.
“Time is an illusion” — no longer applies in the hour of death — or during extra time of a football match.

There is a (confusing) quote from Einstein about the latter mantra. It is a condolence letter dated March 21, 1955, to the son of my deceased Zurich friend Michele Bossi (Christie, 2017):
Now he has also preceded me a little in saying goodbye to this strange world. That means nothing. For us religious physicists, the separation between past, present, and future has only the meaning of an illusion, albeit a persistent one.

These are only words of comfort, not science. The future and the past are (only) information, but the present is active physics (Hehl, 2024). Thus, time is not an illusion, but arguably the most important physical quantity of all, and certainly the most precisely measured.

The most important existing illusion against science is probably:
“Life and spirit exist even without matter.” This includes spirit worlds, spiritualism, and life after death. It is an illusion, factually just superstition.

Is there something outside the real model? Something that is neither physics nor IT? It would be a third world according to Hehl and Popper. This includes, for example, the questions:
“Is true love merely an illusion?” or “Is true art merely an illusion?”
There is probably no simple answer here, and we are at the limits of the scientific world model.

The Austrian author Arthur Schnitzler (1862–1931) wittily assesses disillusionment:
To lose an illusion is to gain a truth. But whoever laments the loss has not been worthy of the gain either.

Conversely, science and technology today create a gigantic number of illusions, primarily with generative AI. There are also three-dimensional illusions in holography. Figure 14 is an example from a technical conference. At the conference venue, the woman is an illusion.

Fig. 14 Hologram of a woman at a conference
Wikimedia Commons, 8oCongresoInnovacion05, Thelmadatter.

In the image, the holographic woman introduces the speakers at the conference: She is an illusion in the room, but real from a distance. The world is becoming increasingly filled with man-made illusions. It is questionable whether these illusions are enriching us.

It is becoming more and more important to understand reality and to distinguish between illusion and reality.