In Defense of Idealism

August 2, 2026 | 13,072 words | 62min read

1. Introduction

Recently, as part of a research practicum, I attended a lecture on epistemology. However, the lecture was not given by a member of the philosophy faculty but by a computer science professor who happened to be interested in philosophical ideas. During the lecture, he presented various epistemological positions, including naïve realism, empiricism, rationalism, idealism, positivism, and others.

He was also very opinionated about these theories. In particular, he was a strong supporter of verificationism and realism and highly critical of what we might call the more “subjective” approaches, such as idealism or constructivism. He repeatedly made fun of people in the humanities, where these theories are more common, arguing that they are ridiculous, that dialectics has long since been proven wrong, that the Weltgeist is a nonsensical concept, and so on. The overall message was essentially: we in STEM are the enlightened ones who know how much better realism is.

I did not say anything at the time. Although I am a computer science student myself, and therefore supposedly on the “better” or “enlightened” side, I found the whole presentation deeply frustrating for several reasons.

First, you are a computer science professor, not a philosopher. I doubt he has carefully read Schopenhauer’s The World as Will and Representation or Berkeley’s A Treatise Concerning the Principles of Human Knowledge. The sheer arrogance of believing that, without seriously engaging with the primary literature, you understand these ideas better than philosophers such as Berkeley, Schopenhauer, or Hegel is astonishing. Whatever objection you have to their theories, do you really think it never occurred to them? These thinkers spent decades developing and defending their positions. Honestly, it often felt as though his understanding of these so-called “subjective” theories came primarily from Bertrand Russell’s History of Western Philosophy, a book that is well known for its rather poor treatment of German idealism.

Second, even if you genuinely believe that your position is correct and that other disciplines are mistaken, I do not understand the need to ridicule them. At one point, he lamented that the gap between STEM and the humanities is widening and predicted that it would continue to do so. But this attitude, mocking rather than sincerely trying to understand the other side, is precisely what keeps that gap from closing.

Third, he spent several slides proudly talking about papers he had written in which he had supposedly “owned” these foolish constructivists. He then recounted the story that one prominent constructivist, Paul Feyerabend, was asked on his deathbed, while suffering in great pain, whether he still believed that pain and medicine were socially constructed, to which he allegedly replied, “No.” Whether the story is even true is beside the point. What struck me was the complete lack of empathy in using someone’s final moments as a punchline to score philosophical points.

Because of all this, I wanted to push back against at least one of the positions that was dismissed so casually. In this article, I want to defend idealism. My goal is to show that idealism is a far more reasonable worldview than it initially appears to someone encountering it for the first time. Although I am not fully convinced by idealism myself, that is not because I believe its arguments are obviously flawed or because the view is too radical. If anything, I think its real challenge is that it may not be radical enough.

I will not discuss every position that was criticized in the lecture. Constructivism, dialectics, and several other theories deserve discussions of their own. However, for the sake of brevity and because idealism is the tradition I know best—I will focus exclusively on idealism.

Before I begin, two caveats are in order.

First, throughout this article I will use terms such as spirit, consciousness, mind, experience, and idea somewhat interchangeably. This is partly because I am highly skeptical of our ability to define such concepts with complete precision. Rather than referring to sharply bounded entities, I think these words evoke overlapping clusters of associations. Moreover, although different philosophers cash out these terms differently, they are often pointing toward something broadly similar. Berkeley primarily speaks of ideas, Schopenhauer emphasizes will, Hegel speaks of mind or spirit, while contemporary philosophers such as Bernardo Kastrup tend to frame the discussion in terms of consciousness or experience.

Second, when I speak of idealism in this article, I primarily have in mind the version that David Chalmers calls cosmic idealism. This is the view that reality does not depend on the mind of any individual subject. Rather, all concrete facts are ultimately grounded in the mental states of a single cosmic mind, such as the universe itself or perhaps God.

2. What is Idealism?

Before mounting a defense of idealism, it is helpful to first define what idealism actually is. The exact definition differs from philosopher to philosopher, so I will only give a rough outline here. Historically, idealism has been associated with philosophers such as Berkeley and Schopenhauer. More recently, philosophers like Bernardo Kastrup have defended modern versions of the view, although they formulate it somewhat differently.

Broadly speaking, however, they all give the same answer to the question: What is reality ultimately made of? Or, put differently, what is the fundamental substance of the universe? Some call it spirit, others mind, experience, or consciousness, but the central idea is the same: reality is fundamentally mental.

To better understand what this means, it is helpful to consider the following distinction. When we reflect on our own experience, we notice (no pun intended) that there seems to be a difference between our outer world and our inner world.

The outer world appears to consist of objective things that exist independently of us, can be measured, quantified, and are accessible to everyone. By contrast, our inner life seems to be subjective, varying from person to person, and directly accessible only to ourselves.

These two “worlds” also appear to possess different properties.

First, objects in the outer world have extension: they occupy a determinate region of space. My desk occupies part of my room and excludes other objects from occupying exactly the same place. This does not seem to be true of the inner world. If I imagine the Eiffel Tower, it does not appear to literally occupy space inside my mind. I can effortlessly shrink or enlarge it, and no matter how large I imagine it to be, I can always imagine something next to it. It does not seem to possess spatial extension in the same sense as physical objects.

Second, the outer world appears to be governed by mechanical laws. If I drop an apple, it falls. Massive objects attract one another through gravity, and physical systems evolve according to regular laws. My imagination, however, does not appear to be constrained in the same way. I can imagine apples floating upward, objects repelling one another, or entirely impossible worlds without contradiction.

Third, the outer world appears to be public, whereas the inner world is private. We can all observe the same tree, hear the same sound, or measure the same temperature. By contrast, no one else can directly observe my thoughts or experiences.

Finally, we have access to these two worlds in fundamentally different ways. We know our inner world through immediate introspection. We simply attend to our own thoughts, sensations, or imaginings. Our knowledge of the outer world, by contrast, is mediated through the senses. Sight, hearing, touch, smell, and taste act as interfaces through which information about the external world reaches consciousness.

Kastrup makes a similar point:

When we look around, we see a world of objects with particular shapes, as well as events unfolding in defined locations. We then automatically assume that the world around us is constituted by these objects and events; by these shapes and locations. In other words, we believe that our perception is a kind of transparent window into the world, revealing to us the world as it is in itself. But can we conceive of perception as something other than a transparent window into the world? Of course we can. Take an airplane, for instance: it has a number of sensors—such as air speed, pressure, and orientation sensors—which measure the states of the sky outside the airplane. The resulting measurements are then displayed to the pilot in an encoded manner, in the form of dial indications in the airplane’s dashboard. As such, the airplane’s dashboard conveys accurate and important information about the sky outside, albeit in an encoded form…

[…]

Instead, perception is like a dashboard of dials: it contains information about the world only in an encoded form, thereby limiting the entropy of our internal states, just as a dashboard of dials intrinsically limits the entropy of information pilots have to contend with.

~ Bernardo Kastrup, Analytic Idealism, Chapter 2

Before we continue, it is helpful to introduce one more important concept: substance.

A substance is the fundamental substrate out of which things are made. One traditional way of defining a substance is as something that exists independently of anything else. For example, we might say that a chair is made of atoms. The chair therefore depends on atoms and is not itself a substance. The atoms, however, would count as substances because they are more fundamental.

Of course, modern physics complicates this picture. Atoms themselves are composed of smaller constituents, which in turn may depend on even more fundamental entities. The example is therefore purely illustrative.

With this terminology, we can distinguish between substances, which are fundamental, and the properties they possess. Ordinary objects are then understood as arrangements of a substance together with its characteristic properties. Again, this is a simplification, but it will suffice for our purposes.

Now that we have distinguished the inner and outer worlds, we can ask an important question: How should we explain this distinction?

This is where the concept of substance becomes useful.

Within ontology, the branch of philosophy concerned with what exists and what things are made of, there are three major positions (strictly speaking there are more, such as Leibniz’s monadology, but these three are the standard views).

The first is dualism, most famously defended by Descartes. As the name suggests, dualism holds that there are two distinct substances: a physical substance underlying the outer world and a mental substance underlying the inner world.

Why might someone be attracted to this view? Precisely because of the differences we just discussed. The physical world possesses extension and appears to follow mechanical laws, whereas the mental world lacks extension and seems fundamentally different. Dualism explains this by saying that these two domains are literally composed of different kinds of substance.

The second position is physicalism (or materialism, I will ignore the distinction here, since philosophers themselves disagree on how best to define physical or matter).

Physicalism is probably the view most people in STEM implicitly grow up with. Its motivation comes largely from the remarkable success of modern science. Time and again, science has explained complex phenomena by reducing them to simpler physical processes. Falling apples, planetary motion, chemical reactions, and biological life have all received increasingly successful physical explanations.

Physicalism therefore argues that the same strategy should apply to the mind. Mental phenomena are not fundamental but instead emerge from physical processes occurring in the brain. There is ultimately only one substance, the physical, and everything mental is reducible to it.

Finally, we arrive at idealism.

In a sense, idealism simply reverses the explanatory direction. Instead of beginning with the physical world and attempting to explain consciousness in terms of matter, idealism begins with consciousness itself. We know our own experiences directly, so the idealist proposes that mentality, not matter, is fundamental. The physical world is then explained in terms of mental substance rather than the other way around.

At first glance this may sound like an outrageous proposal. However, by the end of this article, I hope you will at least see that it is a far more reasonable philosophical position than it initially appears.

To summarize:

• Dualism: there are two fundamental substances, one physical and one mental.
• Physicalism: there is only one substance, the physical, and the mental reduces to it.
• Idealism: there is only one substance, the mental, and the physical reduces to it.

Before we can properly defend idealism, however, there is one final question we must answer: What exactly do idealists mean by “the mental”?

As mentioned earlier, throughout this article I will use terms such as experience, mind, spirit, consciousness, soul, and idea somewhat interchangeably. They are not perfectly synonymous, but they all point toward roughly the same underlying notion.

Here is Berkeley’s explanation:

Besides the endless variety of ideas (objects of knowledge), there is also something that knows or perceives them and performs various operations, such as willing, imagining, and remembering. This perceiving, active being is what I call mind, spirit, soul, or myself. By these words I do not mean any of my ideas, but something entirely distinct from them, in which ideas exist — or, equivalently, through which they are perceived; for the existence of an idea consists in being perceived.

~ Berkeley, Principles of Human Knowledge, Part I, §2.

and

[…] What I am myself, that which I denote by the term I, is the same with what is meant by soul or spiritual substance. If it be said that this is only quarrelling at a word, and that since the immediate significations of other names are by common consent called ideas, no reason can be assigned why that which is signified by the name spirit or soul may not partake in the same appellation. I answer, all the unthinking objects of the mind agree, in that they are entirely passive, and their existence consists only in being perceived: whereas a soul or spirit is an active being, whose existence consists not in being perceived, but in perceiving ideas and thinking. It is therefore necessary, in order to prevent equivocation and confounding natures perfectly disagreeing and unlike, that we distinguish between spirit and idea. See sect. 27.

~ Berkeley, Principles of Human Knowledge, Part I, §139.

For Berkeley, reality consists of spirits and ideas. A spirit is an active, immaterial substance that perceives, thinks, imagines, and wills. It is the subject that has experiences, not itself an object of experience. Ideas, by contrast, are the passive contents of experience e.g. colors, sounds, sensations, and thoughts, which exist only insofar as they are perceived by a spirit. The spirit is therefore the perceiver, while ideas are the things perceived.

Here is a more modern explanation from Kastrup. Notice that he speaks of experience instead of ideas, and consciousness instead of spirit:

When we stand on a hill and look out to the horizon, whatever exists beyond the horizon line isn’t accessible to us—i.e., it isn’t visible. Nonetheless, since we can see the earth up until the horizon, it’s natural to think that, beyond the horizon, there is just more earth; as opposed to something distinct from, and incommensurable with, the earth. Indeed, if someone were to claim that the earth exists only until the horizon, and that beyond the horizon there is something totally distinct from the earth, you would probably question the sanity of the person. In just the same way, the analytic idealist inspects everything they have direct access to and finds only experiential—i.e., mental—states. After all, we are always cooped up in mind. Anything allegedly nonmental, insofar as it can be accessed by us, is perforce a mental abstraction of our own mind. Knowledge itself is a set of experiential states. To put this in the language of our analogy, all we can see until the horizon of personal experience is, well, experience.

~ Bernardo Kastrup, Analytic Idealism, Chapter 6

To put it more simply, and in my own words, we can think of consciousness (or spirit, soul, or mind) as the underlying substance, the stage upon which everything appears. Experiences or ideas are then the contents that appear on this stage, much like actors in a theatre.

The stage determines the general framework within which events can occur, while the actors determine what is actually happening at any given moment. Likewise, consciousness provides the arena in which experience occurs, while particular experiences constitute the ever-changing contents of consciousness.

Naturally, much more could be said about idealism. However, since this article is intended primarily as an introduction and a defense of the view, I have deliberately kept the discussion brief.

3. Three Categories of Arguments

Now that we have defined what idealism is, I want to provide a defense of it. There are several different categories of arguments that can be used in support of idealism. These are not individual arguments, but rather different families of arguments that approach idealism from different perspectives. I will not discuss any of them in exhaustive detail; instead, I will provide a rough outline of each.

Before beginning, I want to add another caveat: not all arguments presented here are direct arguments for idealism. Some are primarily criticisms of physicalism. However, if physicalism fails and dualism is also rejected, then idealism becomes a natural alternative.

To briefly explain why dualism is often excluded from this discussion: in contemporary philosophy, dualism is a minority position, largely because of the famous interaction problem.

The interaction problem asks how two fundamentally different substances, the physical and the mental, could interact with each other. At first glance, this might not seem problematic. However, consider the properties traditionally attributed to these substances. The physical world is described as extended and governed by mechanical laws, whereas the mental world appears to lack extension and does not seem to follow mechanical laws.

How can something that occupies space and follows physical laws affect something that has no spatial extension and is not governed by those same laws? What would the mechanism of this interaction be?

Physicalism and idealism avoid this problem because they posit only one fundamental substance. In physicalism, the interaction problem disappears because mental processes are ultimately physical processes; they exist within the same physical framework and therefore interact according to physical laws.

Idealism similarly avoids the problem, but in the opposite direction: the physical world is not fundamentally separate from the mental world. What we call the physical is ultimately a manifestation of the mental and therefore follows the structure of the mental substance.

3.1 Ontological Defense

Ontology is the branch of philosophy concerned with what exists and what things are ultimately made of. The family of arguments discussed here attempts to identify something that possesses certain characteristics or contains certain features that cannot be explained under physicalism, but can be explained naturally under idealism.

One candidate for such a thing is consciousness.

In the now-famous paper What Is It Like to Be a Bat?, philosopher Thomas Nagel argues that consciousness cannot be fully explained by reducing it to physical processes. From this, some philosophers argue that consciousness poses a fundamental challenge to physicalism.

Very roughly, what defines consciousness? Consciousness can be described as subjectivity: the fact that there is something it is like to be a particular subject. It is the first-person perspective of experience.

To understand the difference between objectivity and subjectivity, we can roughly say that something is objective when there is a fact or answer that exists independently of any particular perspective. Subjectivity, by contrast, concerns the existence of a particular point of view and how reality appears from that perspective.

The problem for physicalism is that it attempts to explain consciousness, a fundamentally subjective phenomenon, by reducing it to something objective. In other words, reduction seems to remove precisely the thing we are trying to explain: subjectivity itself.

Consider Nagel’s example of bat consciousness. We can describe many objective facts about bats. We can explain their sonar system, describe their behavior, and understand that they experience things such as pain, hunger, fear, or desire. However, no matter how much objective knowledge we acquire, we still cannot know what it is actually like to be a bat.

The objective aspects of a bat can be understood from an external perspective because they are features of the world that can be described independently of a particular viewpoint. But the subjective character of the bat’s experience cannot be captured in this way.

This creates a fundamental problem. What does it mean to understand consciousness objectively? If we remove the subjective perspective from a subjective experience and examine it purely from the outside, what remains? What would remain of what it is like to be a bat if we removed the perspective of the bat itself?

Objectification works by removing the particular viewpoint of the observer. We describe things in general terms that are independent of any individual perspective. But consciousness is precisely the existence of a perspective. Any attempt to study consciousness purely objectively seems to move further away from the very thing we are trying to understand.

Reductionism works by explaining phenomena in terms of more fundamental processes and removing the subjective perspective. However, this approach seems inadequate for consciousness because subjective experience is inherently tied to a first-person point of view.

At this stage, this argument is not necessarily an argument against physicalism itself, but rather against the reduction of consciousness. However, since physicalism claims that the physical is fundamental, it must ultimately explain consciousness in terms of physical reality. The question therefore becomes: how can this be done without reducing consciousness to something that excludes the very subjectivity we are trying to explain?

This is where idealism offers a different approach.

For idealism, consciousness is not something that needs to be derived from something else. Consciousness is fundamental. In the same way that mathematics does not explain its axioms through something more fundamental, axioms are the foundation upon which the rest of mathematics is built, idealism treats consciousness as the foundation upon which reality is built.

This would also explain why consciousness has been such a difficult phenomenon to study. The problem is not only that we struggle to discover what consciousness is; we struggle even to define it precisely. This difficulty may arise because consciousness is not an object within reality that can be examined from the outside. Rather, it is the very foundation through which anything can appear.

3.2 Epistemological Defense

The next category of arguments is epistemological. Epistemology is the branch of philosophy concerned with knowledge: how we acquire it, what justifies our beliefs, and what limits our ability to know things.

The epistemological argument for idealism begins by examining the different ways in which we have access to the inner and outer worlds.

As discussed earlier, we appear to have direct access to our inner world through introspection, while our access to the external world is mediated through our senses. The problem is that we know our senses can sometimes deceive us. Optical illusions demonstrate that what we perceive is not always an accurate representation of external reality.

For example, objects at the edge of our visual field can sometimes be misidentified. A person may mistake a coat hanging on a chair for another person, or mistake an object in the corner of a room for something else entirely. Another familiar example occurs when placing an object such as a fork into a glass of water: the fork appears bent where it enters the water, even though we know that the object itself has not changed shape.

These examples show that our sensory experience does not always directly reveal reality as it is. Instead, our senses provide us with a representation of the external world, and this representation can sometimes be inaccurate.

This raises an important question: How can we know that our senses are not always misleading us?

There does not appear to be any argument that can prove with absolute certainty that our sensory experiences always correspond perfectly to an external reality. Any attempt to verify our senses would itself require using our senses, creating a potential circularity.

By contrast, introspection appears to provide a different kind of access. When I experience a thought, feeling, or sensation, I do not infer that I am experiencing it, I directly encounter the experience itself.

Philosopher Philip Goff describes this distinction using the concept of phenomenal concepts: concepts that refer directly to conscious experience itself. These concepts are sometimes described as “opaque” because the experience they refer to cannot simply be translated into an external description without losing something essential.

With this distinction in mind, an argument in favor of idealism can be formulated.

If dualism is rejected, there are two main alternatives: physicalism and idealism.

We seem to have immediate and direct access to the mental world. I do not need to infer that I am conscious; consciousness is the very basis of my experience. However, our knowledge of the external world appears fundamentally different. We do not access the external world directly but only through sensory experiences, and we know that these sensory experiences can sometimes misrepresent reality.

Therefore, we have one domain, our conscious experience, to which we have direct access, and another domain: the external physical world, to which we only have indirect access.

From this perspective, one might ask: should we not prefer the worldview that begins with what we know most directly?

Idealism takes consciousness as fundamental because consciousness is the one thing that cannot be doubted or bypassed. Everything we know about the external world already appears within consciousness. Even our scientific theories, measurements, and observations are themselves experiences within consciousness.

This does not prove idealism by itself. A physicalist can argue that consciousness is a representation of an external physical reality. However, the idealist argues that this reverses the explanatory order. Rather than saying that consciousness somehow emerges from a reality we never directly encounter, idealism begins with the one thing we know directly—experience itself—and explains the apparent external world from there.

3.3 Additional Arguments

The final category consists of several additional arguments and analogies that do not fit neatly into the previous sections.

The Problem of Defining the Physical

The first argument is not directly an argument for idealism, but rather a challenge for physicalism. It concerns the difficulty of defining what exactly the physical, or matter, is supposed to be.

One problem is that our understanding of the physical world has constantly changed throughout the history of science. As scientific progress continues, concepts that once appeared fundamental are often revealed to be composed of something deeper.

For example, some pre-Socratic philosophers argued that the fundamental substance of reality was fire, water, or earth. Later, with the development of atomic theory, matter was understood as consisting of atoms. However, we eventually discovered that atoms themselves are composed of smaller entities, such as electrons, protons, and neutrons, and that these in turn are related to even more fundamental structures.

This raises a difficult question: when we say that reality is fundamentally “physical,” what exactly are we referring to?

If we define the physical based on our current scientific understanding, then history suggests that this definition may eventually become outdated. What we currently consider fundamental may later be revealed to depend on something deeper.

One possible response is to define the physical as whatever future science ultimately discovers to be fundamental. This avoids the problem of scientific progress changing our definition. However, it introduces another difficulty: such a definition becomes difficult, if not impossible, to falsify. If the physical is simply whatever science will eventually discover, then no possible scientific discovery could prove that definition wrong.

This creates a strange situation. The physical becomes something that is always pushed beyond our current understanding: something that exists as the unknown foundation behind our experiences, but whose precise nature remains permanently unclear.

One possible explanation for why defining the physical is so difficult is that the concept itself may be problematic. Perhaps the reason we struggle to define matter is not because we have not yet discovered the correct description, but because matter, as something fundamentally separate from experience, does not exist in the way we assume.

Berkeley makes a similar argument:

(79.) But you will insist, what if I have no reason to believe the existence of matter, what if I cannot assign any use to it, or explain anything by it, or even conceive what is meant by that word? Yet still it is no contradiction to say that matter exists, and that this matter is in general a substance, or occasion of ideas; though, indeed, to go about to unfold the meaning, or adhere to any particular explication of those words, may be attended with great difficulties. I answer, when words are used without a meaning, you may put them together as you please, without danger of running into a contradiction. You may say, for example, that twice two is equal to seven, so long as you declare you do not take the words of that proposition in their usual acceptation, but for marks of you know not what. And by the same reason you may say, there is an inert, thoughtless substance without accidents, which is the occasion of our ideas. And we shall understand just as much by one proposition as the other.

(80.) In the last place, you will say, what if we give up the cause of material substance, and assert, that matter is an unknown somewhat, neither substance nor accident, spirit nor idea, inert, thoughtless, indivisible, immoveable, unextended, existing in no place? For, say you, whatever may be urged against substance or occasion, or any other positive or relative notion of matter, hath no place at all, so long as this negative definition of matter is adhered to.

I answer, you may, if so it shall seem good, use the word matter in the same sense that other men use nothing, and so make those terms convertible in your style. For after all, this is what appears to me to be the result of that definition: the parts whereof, when I consider with attention, either collectively or separate from each other, I do not find that there is any kind of effect or impression made on my mind, different from what is excited by the term nothing.

~ Berkeley, Principles of Human Knowledge, Part I, §79–80.

Berkeley’s point is that if the word “matter” refers to something that cannot be experienced, defined, or understood in any meaningful way, then we may only be using a word without a clear concept behind it.

Kastrup’s Dashboard Analogy

Bernardo Kastrup presents another argument, or perhaps more accurately, an analogy, against treating the physical world as fundamentally separate from consciousness.

His argument is that physicalism may have reversed the relationship between appearance and reality. We assume that the physical world is the external foundation and that consciousness is something produced by it. However, Kastrup argues that what we call the physical world is itself a representation within consciousness.

He explains this using the analogy of an airplane dashboard:

Under Analytic Idealism, the external experiential states that constitute the outside world present themselves to our observation in the form of what we colloquially call the ‘physical’ world, or ‘matter’—i.e., the contents of perception, the stuff we see, hear, smell, taste, and touch. The ‘physical’ world is merely a dashboard representation of the states of the real external world out there, which arise upon our measuring— i.e., observing—the latter’s mental states with our sensors: our eyes, ears, tongue, nose, and skin. Just like an airplane represents the output of its sensors in the form of indications on dashboard dials, we represent the output of our sensors in the form of the ‘physical’ world displayed on the screen of perception. What we colloquially call ‘matter’ is thus merely an internal cognitive representation of the results of measurements performed on mental states. In other words, ‘matter’ is what mental states look like when observed from an outside perspective. And that is all there is to it, in all cases, without exception.

~ Kastrup, Analytic Idealism, Chapter 6

The idea is that an airplane dashboard does not resemble the sky outside the airplane. The dashboard contains numbers, symbols, and indicators that represent information gathered by sensors. A pilot can use this information successfully, even though the dashboard itself does not look like the thing it represents.

Kastrup argues that perception works in a similar way. Our senses measure the world and transform the information into conscious experiences. What we call the physical world e.g. colors, sounds, textures, shapes, and objects, is therefore not necessarily the world as it exists independently of perception. Rather, it is the way reality appears after being processed through our perceptual system.

In other words, matter may not be something fundamentally separate from consciousness. Instead, matter may be what consciousness looks like when viewed from a particular perspective.

Berkeley’s Argument from Extension and Size

A similar argument appears in Berkeley’s discussion of extension and size.

Berkeley challenges the idea that physical properties such as size and extension exist entirely independently of perception. He argues that the size of an object seems to change depending on the observer.

For example, a human and a mite can perceive the same object very differently. A mite’s foot may appear enormous to the mite but tiny to a human. Berkeley asks: which perception represents the object’s true size?

If the object has one objectively correct size existing independently of perception, then one of these experiences must somehow be closer to reality than the other. But what determines which one?

Berkeley argues that this leads to a problem. If extension exists independently of perception, then the same object would somehow need to possess different sizes relative to different observers, which appears contradictory.

A possible response is that the true size of an object is its measurable size, for example, saying that an object is one millimeter long. However, Berkeley’s argument is that measurement only gives us relationships between objects. It tells us that one object is a certain number of units compared with another object, but it does not provide an absolute size existing independently of all possible perspectives.

A human and a mite may both agree that an object is one millimeter long, but that measurement does not capture how that extension appears from their different perspectives.

The deeper point is that space is not merely a mathematical structure of distances and coordinates. Our experience of space also includes how things appear: their size, distance, closeness, and magnitude.

Since these qualities vary depending on the observer, Berkeley argues that there may be no single objective size or extension existing completely independently of perception. What we call the “real size” of an object may instead be an abstraction from different possible experiences of space.

4. Objections

After reading all of this, you might think that idealism is more reasonable than you initially assumed. However, there are still several objections that can be raised. Perhaps there is a flaw in the argument, or perhaps you have a particular intuition that prevents you from accepting idealism.

In this section, I want to address several objections that I find particularly interesting.

4.1 Why Does Idealism Initially Seem So Ridiculous?

The first objection is perhaps the most obvious one: Why does the idea that everything is mental seem so absurd at first glance?

If everything were truly mental, shouldn’t that idea feel much more natural to us?

The first thing to note is that many ideas initially appeared ridiculous or counterintuitive but later turned out to be correct. Einstein famously rejected certain interpretations of quantum mechanics, arguing that “God does not play dice.” A famous response attributed to physicist Niels Bohr was:

“Einstein, don’t tell God what to do.”

Regardless of whether one agrees with the philosophical implications of quantum mechanics, the example illustrates a broader point: our intuitive understanding of reality is not always a reliable guide to what is true. Many scientific discoveries have challenged our everyday assumptions about the world.

A related question connects back to the story from the beginning of this article. Why did the computer science professor dismiss idealism and other philosophical positions as meaningless or absurd?

I want to suggest two additional explanations beyond what I have already discussed.

The Problem of Philosophical Language

First, idealists often use words such as spirit, soul, Weltgeist, mind at large, or world soul. To many modern readers, these words immediately sound mystical, religious, or unscientific.

This can create an automatic rejection before the actual argument has even been considered. The terminology itself triggers associations with supernatural claims, even though many idealist philosophers use these terms in a much more technical philosophical sense.

For example, when Berkeley speaks of spirit, he is not necessarily referring to a religious soul in the popular sense. He is referring to an active subject of experience: something that perceives, thinks, and wills.

Similarly, when Kastrup speaks of mind at large, he is not necessarily claiming that the universe has human-like thoughts or emotions. Rather, he is proposing a metaphysical framework in which consciousness is fundamental.

The words can therefore be misleading if they are interpreted through their everyday associations rather than their philosophical meaning.

Meaning Requires a Framework

The second point is that meaning arises from a framework. Without the necessary background knowledge, a concept, action, or phenomenon can appear completely random and meaningless.

Consider modern art. Many people, when first encountering certain forms of contemporary art, react by saying that anyone could have created it. A famous example is a work consisting of a banana attached to a wall with tape. Without knowledge of the artistic context, movements, and questions being explored, the artwork can appear completely arbitrary.

However, once the viewer understands the framework behind the work, the history of conceptual art, the role of symbolism, and the questions the artist is engaging with, the same object can take on meaning.

A similar thing happens with games. Someone unfamiliar with chess may watch two players move pieces around a board and see only random movements. A chess player, however, understands that a particular move can represent a sophisticated strategy, a sacrifice, or a decisive attack.

The meaning is not contained in the isolated action itself; it emerges from the framework surrounding it.

Oliver Sacks describes a similar phenomenon in An Anthropologist on Mars when discussing Virgil, a man who had been blind since childhood and later regained his sight after more than fifty years. Although Virgil could physically see, his visual experiences initially lacked meaning. He did not immediately understand objects, depth, or spatial relationships because he had not spent his life learning how to interpret visual information.

For example, he struggled to understand where a tree began and ended. When seeing a plane in the sky, he could not immediately understand how something could appear small while actually being far away. Skyscrapers seemed difficult to comprehend because he did not yet understand how such large structures could remain standing.

What was missing was not vision itself, but the conceptual framework that gives visual experience meaning.

The same applies to philosophy. Western philosophy is an ongoing conversation that began with the pre-Socratics and has continued for thousands of years. Each philosopher responds to previous thinkers, inherits their problems, and develops their ideas within an existing intellectual framework.

Idealism should therefore be understood within this tradition. If we remove it from its philosophical context and encounter words such as spirit or mind without understanding the problems they are responding to, the position can easily appear meaningless or absurd.

The initial rejection of idealism may therefore come less from the weakness of its arguments and more from encountering it without the conceptual framework necessary to understand why philosophers were attracted to it in the first place.

4.2 Why Is Physicalism So Popular?

Perhaps the previous section explains why idealism can initially seem strange or even absurd. But even if we understand why we have this intuitive reaction, another question remains:

Why is physicalism the dominant worldview today?

Bernardo Kastrup offers one possible historical explanation. According to him, the rise of physicalism is connected to the historical development of modern science and the desire to separate scientific inquiry from religious authority.

During the Enlightenment, thinkers attempted to establish a method of understanding nature that was independent from theological explanations. However, this created a philosophical problem: everything we directly encounter is ultimately mental.

The colors we see, the sounds we hear, the textures we feel, and even our concept of an external world are all experiences within consciousness. Anything we know about the world already appears within the mind.

Kastrup argues that this created a tension. Science wanted to describe a reality independent of the mind, but everything accessible to us seemed to be inseparable from experience itself.

He describes this problem as follows:

Let us go back to the early Enlightenment years, when members of our budding scientific community needed to carve out some metaphysical ground different from ‘psyche,’ so to avoid persecution by the Church. They were faced with a difficult conundrum for, aside from theoretical abstractions, everything is psychic, experiential, mental, spiritual. Even our perceptions of an external world surrounding us are mental, in the sense of being constituted by experiential qualities such as colors, flavors, scents, textures, etc. Everything touched by the wand of our knowledge—even if only ever so slightly—becomes perforce mental, for our knowledge itself resides in our mind. Anything nonmental is necessarily a conceptual abstraction of our mind, the abstraction itself residing in our mind. We are always cooped up in our own mentation. If there is anything outside it, then it must be brought inside—and thereby immediately become mental—if we are to know it in any sense of the word. Yet, the survival demand placed on the founders of the Enlightenment was precisely to escape their own mentation—for mentation is psyche, the domain of the Church—while pursuing knowledge. How to perform such a magic trick? One possibility was to appeal to second-hand knowledge: things that are known, but not directly by ourselves. Those things, despite being known, are outside our own mind and therefore objective from our perspective. They do exist—for they are known—but without being touched by the wand of our own knowledge. However, this obviously doesn’t work: known things must still exist in a mind, even if not our own mind; even if not a human mind. As such, they still fall within the scope of the psyche, the domain of the Church. Bishop Berkeley’s Subjective Idealism made this abundantly clear, in claiming that the external world exists in the mind of God. What was needed to escape the clutches of the Church was a space outside any mind, even the mind of God. But by looking at the world harder, deeper, all we succeed in doing is extending the scope of our own mentation; and our Enlightenment heroes understood this. What was needed was to forfeit the concreteness of experience and reify, instead, some form of abstraction. The claim would be that, even though the abstraction itself was undeniably mental, it could correctly point to something outside itself, which in turn could be said to be non-mental. This non-mental space would thus fall outside the jurisdiction of the Church. And here is where those quantitative descriptions we talked about earlier suddenly came in handy, very handy indeed! The defining characteristic of the mental is its qualitative nature, i.e., what it feels like to know or be acquainted with something. If a semantic dichotomy could be created—invented, made up, conjured into existence—between qualities on the one hand, and quantities on the other, then our descriptions of reality could be said to have a non-mental character insofar as they are purely quantitative. And hence it was claimed that ‘quality = mind’ and ‘quantity = non-mind.’ Presto! This magic trick is, of course, not only entirely arbitrary and merely semantic, but also self-defeating, as quantities are just mental descriptions of the mental. Nonetheless, it is reasonable to assume that it saved the lives or livelihoods of many a scientist. To this day it remains a core part of our inherited, culture-bound intuitions: just ask yourself > hether you don’t find it rather logical that qualities and quantities form a real dichotomy. And so it was that the absurd notion that quantitative descriptions are fundamentally—i.e., metaphysically, ontologically—distinct from the qualitative world described became enshrined in the highest echelons of our culture. This is how magic is done: through language tricks mistaken for real facts, even—perhaps especially—by those who invent the tricks.

~ Kastrup, Analytic Idealism, Chapter 3

Kastrup’s argument is that one possible solution was to create a distinction between qualities and quantities.

Qualities, such as colors, sounds, tastes, and feelings. were associated with the mind because they are subjective experiences. Quantities, such as measurements, mathematical descriptions, and physical equations, were treated as objective features of reality.

This created a powerful conceptual distinction:

• Quality = mental
• Quantity = non-mental

According to Kastrup, this distinction allowed science to describe a world that appeared independent of consciousness. Instead of dealing with the immediate qualities of experience, science focused on mathematical descriptions of reality.

However, Kastrup argues that this separation may not represent a genuine metaphysical distinction. Quantities are still concepts that exist within consciousness. A mathematical description of reality is itself an experience occurring within the mind.

Therefore, he argues that the distinction between a mental description and a non-mental reality may have been more of a conceptual tool than a discovery about the fundamental structure of reality.

This interpretation is controversial, and it is not the only explanation for the success of physicalism. Many philosophers would argue that physicalism became dominant because physical explanations have repeatedly demonstrated enormous predictive and technological success.

Nevertheless, Kastrup’s point highlights an important philosophical question: Does the success of scientific descriptions prove that the underlying reality is fundamentally non-mental, or does science simply provide an extremely effective description of appearances within experience?

Berkeley makes a similar argument regarding the development of the concept of material substance. He argues that philosophers originally introduced matter because they believed that sensible qualities, such as colors, sounds, and shapes, needed an underlying substance in which they could exist.

However, once philosophers accepted that certain qualities depended on perception, Berkeley argues that there was no remaining justification for preserving matter as a separate underlying substance.

He writes:

It is worth while to reflect a little on the motives which induced men to suppose the existence of material substance; that so, having observed the gradual ceasing and expiration of those motives or reasons, we may proportionably withdraw the assent that was grounded on them.

First therefore, it was thought that colour, figure, motion, and the rest of the sensible qualities or accidents did really exist without the mind; and for this reason it seemed needful to suppose some unthinking substratum or substance wherein they did exist, since they could not be conceived to exist by themselves.

Afterwards, in process of time, men being convinced that colours, sounds, and the rest of the sensible secondary qualities had no existence without the mind, they stripped this substratum or material substance of those qualities, leaving only the primary ones, figure, motion, and such like, which they still conceived to exist without the mind, and consequently to stand in need of a material support.

But it having been shown that none, even of these, can possibly exist otherwise than in a spirit or mind which perceives them, it follows that we have no longer any reason to suppose the being of matter. Nay, that it is utterly impossible there should be any such thing, so long as that word is taken to denote an unthinking substratum of qualities or accidents, wherein they exist without the mind.

~ Berkeley, Principles of Human Knowledge, §73

Berkeley’s argument is that matter was initially introduced as a necessary explanation for perceived qualities. But if those qualities already exist within experience, then the additional concept of an unknown material substrate becomes unnecessary.

In other words, Berkeley argues that philosophers added matter as a hidden foundation behind experience, but when we examine what this foundation actually consists of, we find that it becomes increasingly difficult to define.

The idealist therefore asks:

If everything we ever experience is already mental, and if the supposed non-mental substance behind experience cannot itself be experienced or clearly defined, why should we assume that it exists?

4.3 Are Ordinary Objects Just Ideas?

A common objection to idealism, directly raised against Berkeley, is the following:

If everything is mental, does this mean that ordinary objects are merely ideas in our minds? And if so, how could this possibly be compatible with science?

If idealism is true, does that mean that the sun, mountains, trees, houses, and even our own bodies are nothing more than imaginary objects?

Berkeley responds to this objection by making an important distinction. He does not claim that ordinary objects are illusions or that they exist only as arbitrary creations of our imagination. Rather, he rejects the idea that these objects are made of a separate material substance existing independently of all experience.

He writes:

(34.) First then, it will be objected that by the foregoing principles, all that is real and substantial in Nature is banished out of the world; and instead thereof a chimerical scheme of ideas takes place. All things that exist, exist only in the mind, that is, they are purely notional. What therefore becomes of the sun, moon, and stars? What must we think of houses, rivers, mountains, trees, stones; nay, even of our own bodies? Are all these but so many chimeras and illusions on the fancy?

To all which, and whatever else of the same sort may be objected, I answer, that by the principles premised, we are not deprived of any one thing in Nature. Whatever we see, feel, hear, or anywise conceive or understand, remains as secure as ever, and is as real as ever. There is a rerum natura, and the distinction between realities and chimeras retains its full force. This is evident from sects. 29, 30, and 33, where we have shown what is meant by real things in opposition to chimeras, or ideas of our own framing; but then they both equally exist in the mind, and in that sense are alike ideas.

(35.) I do not argue against the existence of any one thing that we can apprehend, either by sense or reflection. That the things I see with mine eyes and touch with my hands do exist, really exist, I make not the least question. The only thing whose existence we deny is that which philosophers call matter or corporeal substance. And in doing of this, there is no damage done to the rest of mankind, who, I dare say, will never miss it. The atheist indeed will want the colour of an empty name to support his impiety; and the philosophers may possibly find they have lost a great handle for trifling and disputation.

~ Berkeley, Principles of Human Knowledge, Part I, §34–35

Berkeley’s response is that idealism does not remove anything from our experience. The things we see, touch, hear, and interact with remain completely real.

The only thing Berkeley rejects is what philosophers call material substance: the idea that behind our experiences there exists an entirely separate, mind-independent physical substance that somehow causes those experiences.

In other words, Berkeley is not saying:

“The tree in front of me is imaginary.”

Rather, he is saying:

“The tree in front of me is real, but its reality does not consist in being made of an unknown material substance. Its reality consists in being an experienced object within a mental framework.”

This distinction is crucial. There is a difference between saying that something is mental and saying that something is fictional.

A dream is mental but not necessarily real in the same sense as the tree outside my window. The difference is not that one is mental and the other is not. The difference is that one is a private construction of my imagination, while the other is a stable and shared experience that does not depend on my individual will.

For Berkeley, this stability is explained through God. For modern analytic idealists such as Kastrup, it is explained through a broader cosmic consciousness.

Kastrup summarizes this idea:

“In other words, ‘matter’ is what mental states look like when observed from an outside perspective. And that is all there is to it, in all cases, without exception.”

~ Kastrup, Analytic Idealism, Chapter 6

Put into my own words: yes, the sun, the stars, the chair you sit on, and the food you eat are mental. However, this does not mean they are imaginary or unreal.

What appears to us as matter, as something external, solid, and independent, is what experience looks like when it is viewed from the outside rather than accessed through introspection.

When I look at a chair, I do not experience “pure consciousness.” I experience an object with a certain shape, texture, weight, and location. From my perspective, it appears as something external to me. Idealism argues that this external appearance is still ultimately grounded in consciousness.

Importantly, this does not imply that our everyday interactions with the world change.

I can still sit on a chair. I can still eat food and taste it. I can still conduct experiments, make measurements, and develop scientific theories. Idealism does not deny the regularities that science studies.

The distinction is not about how things behave, but about what things ultimately are.

This article is discussing metaphysics and ontology: the fundamental nature of reality. It is not claiming that we should expect different physical behavior under idealism. Metaphysics comes before science in the sense that it concerns the assumptions about what exists that make scientific inquiry possible.

Therefore, idealism is not incompatible with science. In fact, an idealist can fully accept the discoveries of modern physics while simply interpreting their metaphysical meaning differently.

The physical equations, measurements, and predictions remain exactly the same. The disagreement concerns what kind of reality those equations describe.

4.4 If Everything Is Mental, Why Do Things Remain Consistent When I Am Not Experiencing Them?

One final objection concerns the apparent stability of the world.

If everything is mental, and objects only exist as experiences, then why do things continue to exist when I am not perceiving them?

For example, imagine that I light a candle in a room and then leave. When I return several hours later, the candle will have burned down. But if nobody was observing the candle during that time, what explains the fact that the candle continued to exist and change?

This objection relies on a particular interpretation of idealism: the idea that reality exists only within my individual mind. However, this is not the form of idealism defended in this article.

As explained at the beginning, the position discussed here is cosmic idealism. Cosmic idealism does not claim that the external world exists only inside my personal consciousness. Instead, it proposes that reality is grounded in a larger consciousness or mental substrate.

Different philosophers have described this in different ways. Berkeley speaks of God, Hegel speaks of the Absolute or Spirit, and Kastrup uses terms such as mind at large. These terms should not necessarily be understood as referring to a human-like being that thinks thoughts in the same way we do.

Rather, they refer to the fundamental field of experience within which individual experiences occur.

A useful analogy is the ocean and its waves.

The ocean is not a separate object observing the waves from outside. Rather, the waves are patterns that exist within the ocean itself. In the same way, individual conscious experiences can be understood as particular patterns within a larger field of consciousness.

From this perspective, the candle does not stop existing when I leave the room because its existence does not depend on my individual awareness of it. It continues to exist as part of the larger mental reality in which my own consciousness is embedded.

Therefore, the consistency of the world is not a problem for cosmic idealism. The world is not recreated every time an individual mind observes it; rather, individual minds are participating in a larger reality that exists beyond their personal perspective.

5. Possible Advantages of Idealism for Other Problems

So far, we have looked at what idealism is, arguments in favor of it, and possible objections against it. However, I want to strengthen the argument a little further by presenting some possible advantages that adopting this worldview might have.

Naturally, whether these are considered advantages is subjective and depends on one’s interpretation. A consequence only counts as an advantage if one finds that consequence desirable. Nevertheless, these are interesting implications of idealism that are worth considering.

5.1 Skepticism

One possible advantage idealism has over competing theories such as physicalism is that it avoids a collapse into radical skepticism. Why might this be the case?

Let us first examine how we typically arrive at radical skepticism within a physicalist worldview. We notice that our senses sometimes deceive us. Furthermore, we realize that we cannot provide an argument that guarantees that our senses are not always deceiving us.

René Descartes famously illustrated this problem through his thought experiment of the evil demon: imagine a powerful being that systematically deceives us about everything we experience. Perhaps everything we see, hear, and feel is merely an illusion created by this demon. If this possibility cannot be ruled out, then how can we know anything about the external world?

From this, Descartes arrived at the famous insight cogito, ergo sum (“I think, therefore I am”). Even if everything else is an illusion, the very act of doubting proves that there must be something that is doubting. Therefore, Descartes concluded that his own existence was certain.

However, Descartes did not stop there. It was not enough for him to establish that he himself existed; he also wanted to prove that the external world existed. To achieve this, he proposed an argument based on the existence of God: God exists, God is perfectly good, and therefore God would not systematically deceive us.

Naturally, many philosophers reject this argument today, but the important point is that Descartes had to struggle to establish that anything beyond his own mind existed.

Idealism does not face the same problem in the same way because it considers the mental to be fundamental. We have direct access to experience itself. Even if we are mistaken about the external interpretation of our experiences, we cannot be mistaken about the fact that we are experiencing something. The existence of experience does not require an additional proof; it is immediately given.

Berkeley expresses this idea as follows:

Colour, figure, motion, extension and the like, considered only as so many sensations in the mind, are perfectly known, there being nothing in them which is not perceived. But if they are looked on as notes or images, referred to things or archetypes existing without the mind, then are we involved all in scepticism. We see only the appearances, and not the real qualities of things. What may be the extension, figure, or motion of anything really and absolutely, or in itself, it is impossible for us to know, but only the proportion or the relation they bear to our senses. Things remaining the same, our ideas vary, and which of them, or even whether any of them at all represent the true quality really existing in the thing, it is out of our reach to determine. So that, for aught we know, all we see, hear, and feel, may be only phantom and vain chimera, and not at all agree with the real things, existing in rerum natura. All this scepticism follows, from our supposing a difference between things and ideas, and that the former have a subsistence without the mind, or unperceived.

~ Berkeley, Principles of Human Knowledge, §87

Berkeley’s argument is that skepticism arises specifically because we assume there is a distinction between our experiences and a separate external reality that exists independently of them. If we believe that our perceptions are merely representations of something hidden behind experience, then we can always ask whether those representations accurately correspond to the hidden reality.

Idealism removes this gap. The experienced world is not a copy of something completely separate from experience; rather, experience itself is the fundamental reality.

5.2 The Existence of God

For Christians and other religious traditions that face uncertainty about the existence of God, idealism can offer a possible foundation for a spiritual worldview.

The cosmic mind, whether called the Weltgeist, Weltseele, “mind at large,” or something else, can be identified with God. This is the position taken by Berkeley, who is a cosmic idealist: he argues that the cosmic entity in which all mental, spiritual, and experiential states exist is the Christian God.

Of course, idealism does not prove the existence of God. Rather, it provides a metaphysical framework in which the existence of a divine mind is more natural than in a purely materialist worldview.

5.3 Less Cosmic Worship or More Worship?

Berkeley proposes the following argument against the worship of natural objects:

The existence of matter, or bodies unperceived, has not only been the main support of atheists and fatalists, but on the same principle doth idolatry likewise in all its various forms depend. Did men but consider that the sun, moon, and stars, and every other object of the senses, are only so many sensations in their minds, which have no other existence but barely being perceived, doubtless they would never fall down, and worship their own ideas, but rather address their homage to that eternal invisible Mind which produces and sustains all things.

~ Berkeley, Principles of Human Knowledge, §94

Berkeley argues that if people understood that objects such as the sun, moon, and stars are not independent material substances but rather experiences sustained by a greater mind, then they would not worship these objects themselves. Instead, they would direct their worship toward the eternal mind responsible for sustaining them.

However, one could also interpret this differently. Since the sun and stars are still expressions within the cosmic mind, they could be understood as manifestations or “avatars” of this greater mind, similar to certain interpretations found in Hinduism. Nevertheless, under idealism, the sun and stars would not have a fundamentally privileged status compared to a chair, a banana, or any other object. They are all expressions of the same underlying reality.

5.4 Easier Christian Resurrection

Berkeley proposes another consequence of idealism regarding the Christian doctrine of resurrection:

The same absurd principle, by mingling itself with the articles of our faith, hath occasioned no small difficulties to Christians. For example, about the resurrection, how many scruples and objections have been raised by Socinians and others? But do not the most plausible of them depend on the supposition, that a body is denominated the same, with regard not to the form or that which is perceived by sense, but the material substance which remains the same under several forms? Take away this material substance, about the identity whereof all the dispute is, and mean by body what every plain ordinary person means by that word, to wit, that which is immediately seen and felt, which is only a combination of sensible qualities, or ideas: and then their most unanswerable objections come to nothing.

~ Berkeley, Principles of Human Knowledge, §95

I will not comment further on this argument, but it may be an interesting implication for Christian philosophers.

5.5 Theory of Time

One final possible advantage concerns the philosophical problem of time. The nature of time is an extremely complex topic in philosophy. A famous distinction is between A-theory and B-theory of time.

Very roughly, A-theory views time as having an objective flow: the present moment is fundamentally different from the past and the future. B-theory, in contrast, views time as a static structure where past, present, and future events all exist equally, and the feeling of temporal flow is a feature of consciousness rather than reality itself.

These two views create difficult philosophical problems, and I will not go into detail here. For anyone interested, McTaggart’s argument for the unreality of time is a famous starting point.

One possible solution is eternalism: the view that all moments of time exist equally. Under eternalism, the universe can be understood as a four-dimensional structure in which past, present, and future events all exist.

Eternalism fits naturally with idealism because time itself can be understood as a feature of experience rather than a fundamental property of reality.

Kastrup gives an interesting example to illustrate this point. As a child, he observed his father playing chess against himself, a common training technique before computerized chess engines. His father would make a move with the white pieces, rotate the board by 180 degrees, then make a move with the black pieces.

The interesting question is: what would happen if we could alter his perception of time so that all experiences from the white side were connected into one continuous stream, while all experiences from the black side were connected into another? His father would then have a continuous memory of playing one game as white and another game as black, believing that two different players had participated.

From the perspective of each stream of experience, the other side of the game would appear to belong to another person. The fact that both perspectives belong to the same person would not be directly accessible from within either perspective.

Kastrup describes a similar phenomenon from his own experience with anesthesia:

A few years ago, I had to undergo a simple, short, but very painful medical procedure. So instead of pumping me full of opioids, the doctors decided to give me a fairly small dose of a general anesthetic, which would knock me out for about 15 minutes. I figured that this would be a fantastic opportunity for an experiment: I would try to focus my attention introspectively and fight the effects of the drug for as long as I could, so to observe the subjective effects of the anesthetic. […]

The drug had altered my perception of time in a very specific and surprising way. If we visualize subjective time as a string from where particular experiences—or, rather, the memories thereof—hang in sequence, the drug had not only distorted or eliminated access to some of those memories, but also cut off a segment of the string and tied the two resulting ends together, so as to produce the impression that the string was still continuous and uninterrupted.

~ Kastrup, Analytic Idealism, Chapter 8

The point Kastrup draws from this is that subjective time is not necessarily a direct reflection of an external physical timeline. Our experience of time can be manipulated without leaving any noticeable trace from within consciousness itself.

Under analytic idealism, this is expected: the physical world is not the fundamental reality but rather the representation of reality from a particular perspective. Therefore, space and time themselves are features of the perceptual interface rather than fundamental properties of existence.

6. Why I believe the argument does not quite go through

One of the strongest arguments in favour of idealism concerns epistemology. The argument begins with an apparent asymmetry: our knowledge of the external world is always mediated through our senses, and we know from experience that our senses can deceive us. In contrast, our knowledge of our own mind appears to be direct and immediate. I do not discover my thoughts, emotions, and experiences through observation in the same way that I discover external objects; they seem to be given to me directly. From this, thinkers such as Schopenhauer, Bernardo Kastrup, and Philip Goff argue that consciousness occupies a privileged epistemological position and therefore should be regarded as fundamental.

However, I am somewhat suspicious of the assumption that we have completely direct access to our own mind. This assumption seems to rely on a traditional picture of the mind as a unified inner observer that simply receives and observes its own contents. Modern cognitive science gives us reasons to doubt this picture.

For example, in Why Buddhism Is True, Robert Wright discusses the idea that the mind is not a single unified entity but rather a collection of different cognitive systems, each with its own goals, desires, and evolutionary functions. One system may be responsible for seeking social status, another for hunger, another for reproduction, another for avoiding danger, and so on. These different systems can compete with each other, and what we experience as a unified self may actually be the result of many interacting processes.

If this picture is correct, then we must ask: what exactly is the thing that supposedly has direct access to the mind? If the mind itself is composed of many different processes, then the relationship between the observer and the observed becomes much less straightforward. Perhaps there is no single inner subject that simply perceives mental states, but rather a complex system continuously constructing an interpretation of itself.

A related example comes from split-brain experiments. In these experiments, researchers found that when the two hemispheres of the brain are separated, one hemisphere can initiate an action while the speaking hemisphere, which lacks access to the true cause of the action, often produces a plausible explanation afterwards. Rather than admitting ignorance, the mind appears to generate a coherent narrative explaining behaviour that was not actually consciously initiated by that part of the brain.

One possible interpretation of this is that the ego functions partly as a kind of “public relations system.” Humans are social creatures, and in a social environment it is valuable to be able to explain and justify our actions. A person whose behaviour appears completely random is difficult to trust because their future actions become unpredictable. A coherent self-narrative therefore has an important social function: it allows both ourselves and others to understand our behaviour within a framework of reasons, goals, and values.

This raises a problem for the epistemological argument from idealism. If our own mental life is not simply transparent to ourselves, but is instead constantly interpreted and reconstructed by different cognitive systems, then the contrast between “direct knowledge of the mind” and “indirect knowledge of the external world” becomes less clear.

Consider a simple example: imagining a triangle. It may seem that there is a single subject that directly observes the mental image of the triangle. However, from the perspective of cognitive science, this experience may instead arise from the interaction of many different neural processes responsible for memory, visual imagination, attention, language, and interpretation. The experience feels immediate, but the mechanisms producing it are highly complex and hidden from introspection.

We can observe something similar in everyday perception. The meaning and significance of an object can change depending on our emotional state, memories, expectations, or current goals. A person we perceive as threatening in one context may appear harmless in another. A place associated with painful memories may feel completely different from the same place experienced under different circumstances. Our experience of the world is therefore not merely a passive reception of reality, but an active process of construction and interpretation.

This does not prove physicalism. The fact that consciousness depends on complex cognitive processes does not automatically show that consciousness is reducible to matter. The hard problem of consciousness remains: explaining why physical processes should give rise to subjective experience at all. However, modern cognitive science does challenge a simpler form of idealist reasoning that assumes consciousness is immediately and transparently accessible to itself.

The more we understand about the mind, the less plausible the traditional image of a unified inner observer becomes. Instead, we find a dynamic system of interacting processes that continuously construct our experience of ourselves and the world. Therefore, while idealism may still provide a possible metaphysical framework, the epistemological argument based on privileged access to the mind may not be as decisive as it first appears.

7. Why the question is not so important

In the end, I do not think the question of idealism versus physicalism matters as much as people often assume. Metaphysical positions can have certain consequences or provide different ways of interpreting reality, but most of these consequences are not, in my view, significant enough to justify treating metaphysical debates as the central questions of human existence.

Furthermore, there is a fundamental difficulty in doing metaphysics: our language evolved to describe everyday human experiences within the world, not to describe the ultimate structure of reality. When we attempt to talk about something beyond our ordinary categories, we inevitably run into problems. Our concepts may simply not be adequate for describing whatever reality ultimately is. In addition to this limitation of language, there are also limitations inherent in human cognition itself. Just as a dog cannot understand calculus because of the limits of its cognitive architecture, there may be aspects of reality that humans are simply not equipped to fully comprehend.

However, the most important point is a practical one. Regardless of whether idealism, physicalism, dualism, or another metaphysical theory is correct, most people ultimately want similar things: to be happy, to reduce suffering, to live meaningful lives, and to understand how they should act. For these goals, practical wisdom and psychological insight seem far more important than theoretical speculation about the fundamental nature of reality.

This might seem contradictory, given that most articles on this website are theoretical in nature. However, I see these philosophical investigations as a foundation. I have several more theoretical articles planned, because I want to complete this philosophical framework, but the purpose of such a framework is ultimately practical. Philosophy should not merely be an intellectual exercise; it should influence how we understand ourselves and how we live.

I am also not particularly emotionally invested in the idealism versus physicalism debate. I am certainly more interested in it than the average person, simply because I have spent a lot of time studying it, but I do not have a strong attachment to either side. If tomorrow convincing evidence showed that physicalism was correct, or that idealism was correct, I would not feel personally threatened by either conclusion. The original motivation for writing this article was not a desire to defend idealism at all costs, but rather a reaction to the arrogance of the professor mentioned at the beginning of the article: his complete certainty about his worldview, his lack of doubt, and his dismissive attitude towards philosophical questions that he did not understand.

A story from Buddhism illustrates this attitude well:

It’s just as if a man were wounded with an arrow thickly smeared with poison. His friends & companions, kinsmen & relatives would provide him with a surgeon, and the man would say, ‘I won’t have this arrow removed until I know whether the man who wounded me was a noble warrior, a priest, a merchant, or a worker.’ He would say, ‘I won’t have this arrow removed until I know the given name & clan name of the man who wounded me… until I know whether he was tall, medium, or short… until I know whether he was dark, ruddy-brown, or golden-colored… until I know his home village, town, or city… until I know whether the bow with which I was wounded was a long bow or a crossbow… until I know whether the bowstring with which I was wounded was fiber, bamboo threads, sinew, hemp, or bark… until I know whether the shaft with which I was wounded was wild or cultivated… until I know whether the feathers of the shaft with which I was wounded were those of a vulture, a stork, a hawk, a peacock, or another bird… until I know whether the shaft with which I was wounded was bound with the sinew of an ox, a water buffalo, a langur, or a monkey.’ He would say, ‘I won’t have this arrow removed until I know whether the shaft with which I was wounded was that of a common arrow, a curved arrow, a barbed, a calf-toothed, or an oleander arrow.’ The man would die and those things would still remain unknown to him.[1]

The point of this story is not that questions about reality are meaningless. Rather, it is a warning that intellectual curiosity can become a distraction when it replaces attention to the problems immediately in front of us. Understanding the ultimate nature of reality may be interesting, but it does not automatically make us wiser, kinder, or happier.

If one nevertheless feels the need for a metaphysical framework, one possibility I find particularly interesting is process philosophy, especially the work of Alfred North Whitehead. Process philosophy begins with a simple observation: everything we encounter is constantly changing. Nothing in experience appears to be a completely static, unchanging substance. From this starting point, Whitehead develops a metaphysics in which processes, events, and relations are more fundamental than permanent objects.

Compared with traditional substance-based metaphysics, this approach seems intuitively closer to the reality we actually experience. The world does not appear to us as a collection of fixed things that occasionally undergo change; rather, it appears as an ongoing process of becoming. Whether process philosophy is ultimately correct is another question, but it offers a valuable perspective: perhaps reality is not something made of things that change, but something fundamentally composed of change itself.

Perhaps the most important philosophical lesson is not discovering the final substance behind reality, but recognizing the limits of our certainty and remaining open to the possibility that reality is stranger than our intuitions suggest.

Resources

Books

• René Descartes — Meditations on First Philosophy
• Bernardo Kastrup — Analytic Idealism
• George Berkeley — A Treatise Concerning the Principles of Human Knowledge
• Robert Wright — Why Buddhism Is True

Papers

• David Chapman — Idealism and the Mind-Body Problem
• Thomas Nagel — What Is It Like to Be a Bat?
• J. E. McTaggart — The Unreality of Time

Talks

• Philip Goff — Why I Am a Heretical Christian
• Bernardo Kastrup — Why Materialism Is Complete Nonsense
• Keith Frankish — Could Consciousness Be an Illusion?
• Sam Harris — Spirituality for Atheists
• Swami Sarvapriyananda — Hinduism, Consciousness and Advaita Vedanta

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