Quick Answer
A genuinely serious philosophical argument wearing a title designed to lose it a hearing. Kastrup's position is that consciousness is all there is, that matter is what mental activity looks like from outside, and that we are dissociated segments of one field of experience. He engages the neuroscience directly rather than avoiding it, which most idealists do not. The dissociation analogy is carrying more weight than the clinical evidence can support, and that is the place to press.
Key Takeaways
- Not the claim that the world is imaginary. Kastrup rejects that reading forcefully.
- He engages brain damage and anaesthesia head on, which is the test most idealism fails.
- The dissociation analogy is the load-bearing move and the weakest link.
- Idealism has its own hard problem: explaining why experience is lawful and shared.
- The title is a liability, and his later academic books are the better version.
🕑 15 min read
What This Book Is
Why Materialism Is Baloney was published in 2014, with the subtitle explaining that it concerns how some sober scientists have been fooled into believing in the world of matter.
It argues for idealism: the position that consciousness is the sole fundamental reality and that the physical world, including brains and bodies, is how certain mental processes appear when observed from a particular vantage point.
What separates it from most writing in this vein is that it argues. Kastrup does not appeal to mystical experience, does not invoke quantum mechanics as a licence for anything, and takes the standard scientific objections seriously enough to answer them one at a time.
On the title. It is a marketing decision and a bad one. The book is more careful than the cover, and readers who would engage with the argument frequently do not get past it. This review treats the argument rather than the packaging.
Who Bernardo Kastrup Is
Kastrup holds doctorates in computer engineering and in philosophy. Before turning to philosophy full time he worked at CERN and in the technology industry, in artificial intelligence and reconfigurable computing.
That background is relevant in two ways. He is not scientifically naive, and he cannot be dismissed as someone who does not understand what he is arguing against. And his engineering habits show in the writing: he defines terms, states his position formally, and works through objections in order.
He has since published a series of increasingly academic books, defended the position in peer-reviewed philosophy journals, and become the most visible contemporary advocate of idealism in the English-speaking world.
This is his most popular and most polemical book. The later ones are better argued and less fun.
What He Is Not Claiming
Necessary before anything else, because the position is misidentified almost universally.
He is not saying the world is imaginary or that objects vanish when unobserved. The world is entirely real and behaves lawfully.
He is not saying your mind creates reality. Individual minds are, on his account, small dissociated portions of something vastly larger, and they no more create the world than a dream character creates the dream.
He is not saying that thinking differently changes physical facts. The regularities we call physical law are not responsive to intention, which is precisely why they look like an external world.
He is not making a quantum-mechanical argument. He mentions physics and does not rest the case on it.
What he is saying is a metaphysical claim about what the world is made of, and it leaves every scientific finding exactly where it was.
The Problem He Starts From
The argument begins with a difficulty that is not his invention and is widely acknowledged.
Physical description characterises things in terms of structure, function and relation: what something is made of, how its parts are arranged, what it does under what conditions. That vocabulary is enormously powerful and it is complete for its purposes.
The problem is that no amount of it appears to yield experience. You can specify every physical fact about a system processing light of a certain wavelength and nothing in that specification says why there is something it is like to see red. The gap between the two vocabularies is what is called the hard problem, and it is a genuine open question in philosophy of mind rather than a fringe complaint.
Kastrup's move is to argue that this gap is not a difficulty to be solved but a symptom of a wrong starting assumption. If you begin with matter and try to derive experience, the derivation cannot be made to work. So begin with experience.
The Position Itself
Stated as directly as he states it.
There is one field of consciousness, which he sometimes calls mind at large. It is not a person, has no plan, and is not a deity in any conventional sense.
Within it, dissociation occurs: portions become walled off, unable to access the rest, and each such portion is a subject with an apparently private inner life. You are one of those.
What such a portion perceives, when it looks outward, is the rest of the field, and what mental processes look like from outside a dissociative boundary is what we call matter.
So the physical world is not something other than consciousness. It is the appearance consciousness has when viewed across a dissociative boundary, and the brain is what a dissociated portion looks like from outside.
He is careful about the final point: the brain is the image of a mind, not its cause, in the same way that a photograph of a fire is an image of combustion rather than the thing burning.
The Dissociation Argument
This is the innovation and the reason the book was taken seriously by people who dismiss idealism generally.
The standard objection to any one-mind view is obvious: if reality is a single consciousness, why are there many apparently separate subjects who cannot read each other's thoughts?
Kastrup's answer is empirical rather than speculative. Dissociation is a documented phenomenon. In dissociative identity disorder, a single human being presents multiple alters with distinct memories, distinct self-conceptions, and no access to each other's mental contents. Some alters do not know the others exist.
He notes reports of physiological differences between alters in the clinical literature, including cases in which measurable functional changes accompany a switch.
His argument is that this establishes a proof of concept: a single conscious subject can, without ceasing to be one, produce multiple centres of experience genuinely walled off from each other. If that occurs within one human mind, the same mechanism at cosmic scale would produce exactly the situation we find.
Whatever you make of the conclusion, this is a good example of how to do metaphysics well. Kastrup identified the strongest objection to his own position, went looking for an empirical phenomenon that would show the required mechanism is possible, and built the argument on it rather than on assertion. That is a considerably higher standard than most positions in this area meet, including some that are more respectable. The question then becomes whether the phenomenon can bear the weight, which is a much better question to be arguing about.
The Whirlpool Image
His central metaphor and it is genuinely clarifying.
Consider a whirlpool in a stream. It has a location, a shape, a duration, and it can be pointed at and named. It is also not a thing separate from the water; it is a pattern the water is doing, and there is no whirlpool-stuff distinct from water.
When the whirlpool dissipates, nothing is destroyed. The water remains. What ends is a localised pattern of movement.
On Kastrup's account, a person stands to consciousness as a whirlpool stands to water. You are a localised pattern of activity within a field, with real boundaries and a real duration, and not a separate substance.
The image does considerable work. It makes individuality real without making it fundamental, and it gives an account of death that is neither annihilation nor personal survival: the pattern ends and the field does not, and whether that is consoling depends entirely on what you took yourself to be.
The Brain Objection
The standard reply to any idealism is that we know the brain produces consciousness because damage to it changes consciousness in specific, predictable ways.
Kastrup's response is that correlation is exactly what his position predicts and is not evidence for generation.
If the brain is the appearance of a dissociated mental process, then changes in that process will show up as changes in its appearance, and interfering with the appearance will correspond to interference in the process. The relationship is one of image to thing imaged, and images track what they image.
He compares it to a fire and its heat signature on a thermal camera. Alter the fire and the image changes. Block part of the camera's view and the recorded image changes. Neither shows that the image is producing the fire.
This is a legitimate reply and it is the standard idealist move. What it establishes is that the correlation does not by itself settle the question, which is true. What it does not establish is that idealism is the better explanation, and this is where the argument becomes a comparison of theoretical virtues rather than a matter of evidence.
Brain Damage and Anaesthesia
He goes further than most idealists here and the material deserves engagement.
Kastrup notes a class of cases in which reduced brain activity is associated with reported enrichment rather than impoverishment of experience: some psychedelic imaging results showing decreased activity in certain networks alongside dramatically intensified experience, reports of unusual lucidity in some near-death circumstances, and the phenomenon of unexpected clarity shortly before death in people with advanced dementia.
His argument is that a straightforward generation model predicts less brain activity means less experience, and these cases run the other way, which is more comfortable for a filter or localisation model than for a production model.
The counter-arguments are real. Decreased activity in one network does not mean decreased activity overall, and can mean disinhibition elsewhere. Reports of intensity are self-assessments made afterwards. The dementia cases are documented and rare and not well understood by anyone.
The honest position is that these are genuine anomalies for a simple production account, that they are not decisive, and that Kastrup presents them with somewhat more confidence than the data support.
Idealism's Own Hard Problem
The objection I find most serious and which the book does not fully meet.
Materialism struggles to explain why physical processes are accompanied by experience. Idealism has a mirror difficulty: why does experience take the specific, regular, lawful, shared forms it does?
If everything is mind, why is the world not more like a dream? Why does it have stable physics, why do measurements agree between observers, why can predictions be made decades in advance and confirmed, and why do the regularities hold whether or not anyone is attending to them?
Kastrup's answer is that mind at large has its own inherent dispositions and that what we call physical law is a description of them, and that these operate below the level of anything like will or intention.
That is coherent and it is close to a restatement. Saying that the regularities exist because the underlying reality has regular dispositions explains the regularity by naming it. Materialism does the same thing with its own bedrock, which is a fair point in reply, and neither side gets to claim the advantage.
Where the Analogy Strains
The critical point, and it is where a sceptical reader should concentrate.
The dissociation argument is doing enormous work, and the clinical phenomenon it rests on is being extended a very long way.
In the clinical case, alters share a body, a brain, a history and a sensory apparatus. They alternate rather than coexisting in parallel, and the boundaries are permeable in documented ways. The condition is understood as a response to trauma in a developing mind.
What Kastrup needs is billions of simultaneous, stable, lifelong dissociations, each with its own sensory perspective on a shared world, with boundaries that never leak in any reliably demonstrable way, and with no developmental history to explain their formation.
That is not a scaling-up of the clinical phenomenon. It is a different thing that shares a name.
The diagnostic status and mechanisms of dissociative identity disorder are themselves debated within psychiatry, which makes it an uncertain foundation for a metaphysics.
None of this refutes idealism. It does mean the argument's most distinctive support is weaker than presented.
Against Panpsychism
Worth covering because the two positions are frequently confused and Kastrup is sharp on the difference.
Panpsychism holds that consciousness is fundamental and distributed: elementary physical constituents have some minimal experiential character, and complex experience is built from them.
Its notorious difficulty is the combination problem. How do many tiny subjects of experience combine into one unified subject? Your experience is not a committee of trillions of micro-experiences; it is a single field. Nobody has given a satisfying account of the transition.
Kastrup argues idealism avoids this by starting from unity. There is one field and the question is how it divides, which he claims is the easier problem because division has an observed mechanism in dissociation.
The objection in reply is that he has traded a combination problem for a decomposition problem and that the second is not obviously easier, since the specific pattern of divisions, one per organism, stable over a lifetime, is exactly what needs explaining and dissociation does not explain it.
The Tone Problem
A fair review has to address the register, because it affects who reads the book.
Kastrup is combative. Materialists are described as fooled, as holding a position that is obviously incoherent, as failing to see what should be evident. The rhetoric is confident throughout.
The cost is that argument and assertion become hard to distinguish. When the same emphatic register carries a well-supported point and a contested one, a reader cannot easily tell which is which without doing the work themselves.
It also loses him the audience most worth persuading. Academic philosophers who might engage with analytic idealism are given a title and a tone that make dismissal easy, and dismissal is what largely happened.
His later books correct this substantially. If you want the position at its strongest, the more recent academic treatments are where to find it, and this book is where to find it at its most readable.
Who Should Read It
Read it if you find the standard account of consciousness unsatisfying and want the strongest contemporary alternative stated as an argument rather than an intuition.
Read it if you are interested in what consciousness is and want to see how the question looks when the usual starting assumption is reversed.
Read it alongside Hoffman, who reaches a nearby destination by an entirely different route, and alongside Nagel for a more cautious statement of the same dissatisfaction.
Do not read it expecting a neutral survey, and do not treat the confident tone as a measure of how well any particular point is supported. And if you find the argument persuasive, read the objections properly rather than accepting his versions of them.
What this argument does not license. Idealism as Kastrup defends it makes no claim that individual minds control physical events, that illness is mental in origin or curable by belief, or that medical treatment is optional. He is explicit that the regularities of the world are not responsive to personal intention, and his position is a claim about what reality is made of rather than about what you can do to it. Material citing him for the opposite is misrepresenting him.
Set the metaphysics aside and one thing here is worth keeping. Kastrup's argument depends on noticing an assumption almost nobody examines: that the world is fundamentally made of stuff, and that experience is a puzzle to be explained in terms of stuff. That is not an observation. It is a framework inherited from a particular period, held so widely that it has become invisible, and treated as the neutral background against which theories are judged. You can decline his conclusion and still benefit from seeing that the starting point was a choice. Most of what feels like obvious common sense about the nature of things is a settlement reached by other people, some time ago, for reasons you have never examined.
A serious argument with an unserious title.
Affiliate disclosure: Thalira earns a small commission on purchases made through the link above, at no additional cost to you. Our view that his later academic books make the case better is set out above and is independent of the link.
Frequently Asked Questions
What is Why Materialism Is Baloney about?
Bernardo Kastrup's 2014 argument that consciousness is the sole fundamental reality, that the physical world is how mental processes appear from a particular perspective, and that individual minds are dissociated segments of a single field of experience.
Who is Bernardo Kastrup?
A Dutch-Brazilian writer with doctorates in computer engineering and in philosophy, who worked at CERN and in the technology industry before turning to philosophy of mind full time. He is the most prominent contemporary advocate of idealism.
What is analytic idealism?
His term for the position that reality is fundamentally mental, defended by argument rather than by mystical appeal. It is not the claim that the world is imaginary or that individual minds create it, and Kastrup is emphatic about both distinctions.
What is the dissociation argument?
That individual minds are like the separate personalities in a dissociative identity disorder: genuinely walled off from each other while belonging to one underlying subject. He points to the clinical literature to argue that a single consciousness can produce apparently separate centres.
How does he explain the physical world?
As appearance. On his account matter is what mental processes outside your own dissociation look like when observed from within it, in the same way that brain activity is what a person's inner life looks like from outside rather than being that inner life.
What is the hard problem?
The question of why physical processes should be accompanied by subjective experience at all. Kastrup argues that materialism cannot answer it in principle, and that idealism dissolves it by never introducing the gap between physical and experiential in the first place.
What are the strongest objections?
That the dissociation analogy is doing more work than clinical evidence supports, that idealism faces its own version of the hard problem in explaining why experience takes the regular lawful forms it does, and that the tone substitutes for argument in places.
Does he engage with neuroscience?
Yes, and this is a genuine strength. He addresses brain damage, anaesthesia and correlations between neural activity and experience directly, arguing that correlation is what his position predicts and does not establish that the brain generates consciousness.
Is the title a problem?
It costs him readers he would otherwise persuade. The argument inside is considerably more careful than the cover suggests, and academic philosophers who would engage with the position are given an easy reason not to.
How does it relate to panpsychism?
They agree that consciousness is fundamental and disagree about structure. Panpsychism distributes small experiences among many physical things and must explain how they combine. Kastrup starts with one field of experience and must explain how it divides.
Which of his books should you read?
This one is the most accessible statement of the position and the most combative. His later academic work states the same case more carefully, with fuller engagement with the philosophical literature, and is the better choice for a critical reader.
Who should read it?
Anyone who finds the standard physicalist account of consciousness unsatisfying and wants the strongest contemporary alternative argued rather than asserted, and anyone interested in a serious idealist position defended in modern terms.
The starting point was always a choice
Whether or not Kastrup is right, the useful thing he does is make visible a decision that was taken before you arrived. Somebody, at some point, settled on matter as the thing that is really there and experience as the thing that needs explaining, and four centuries later that settlement is presented as the plain view of anyone sensible. It might be correct. It is not obvious, it is not neutral, and the people who chose it had reasons that were about the physics they were doing rather than about consciousness at all. You are entitled to hold the question open, and holding it open is not the same as believing anything in particular.
Sources & References
- Kastrup, Bernardo (2014). Why Materialism Is Baloney. Iff Books.
- Kastrup, B. The Idea of the World and later academic statements of analytic idealism.
- Chalmers, David. On the hard problem of consciousness.
- Clinical literature on dissociative identity disorder and its contested status.
- Imaging research on reduced network activity under psychedelics.
- Philosophical literature on the combination problem in panpsychism.