This article was written in response to Bernardo Kastrup's article 'The Mysterious Disappearance of Consciousness'

Bernardo Kastrup is mystified by the view of consciousness that has come to be known as illusionism. He describes it as a “mind-bogglingly extraordinary claim”, which seems to be, simply, “nonsense”. He’s not alone. The philosopher Galen Strawson has called it “the silliest claim ever made” and likened it to Flat Earth theory, and I’ve no doubt that many others would agree.

It seems to these people that illusionists such as myself are saying something utterly ridiculous — that we’re claiming that people are not conscious, don’t have experiences, don’t see or hear, don’t feel pain or emotion, don’t have an inner life. What’s going on? How could we possibly believe that, and, if we don’t, how could highly intelligent people such as Kastrup and Strawson have so radically misunderstood what we do mean? This is, Kastrup says, “an authentic and rather baffling mystery”, and I shall now attempt to shed some light on it.

The basic explanation is simple; illusionists don’t deny that we are conscious. It is true that some interviews with me have appeared under titles that suggest otherwise, but I always make it clear that my target is a much more specific claim, as I shall now explain. There’s a straightforward sense in which we obviously are conscious, and indeed I describe illusionism as a theory of consciousness. What illusionists reject is a certain conception of what consciousness is. However, this conception is so deeply rooted in our way of thinking that, to many people, denying it is equivalent to denying the existence of consciousness itself.

What illusionists reject is a certain conception of what consciousness is

As these people see it, there is a stark and simple choice: endorse that conception or deny that consciousness exists. There is no third option, and anyone who sincerely believes there is must be confused and self-deluded. Of course, there might not be a third option, and, even if there is, it might not be an attractive one. But that needs to be argued. To assume at the start that there isn’t and that illusionists are denying the existence of consciousness is to assume the answer to the very point at issue (to beg the question in philosophical parlance). Let me explain what the option is supposed to be, so that you can judge for yourself.

I’ll start with a description of the sense in which we undoubtedly are conscious. It’s this. Our lives are filled with conscious experiences — episodes of seeing, hearing, smelling, tasting, feeling, and of having bodily sensations of various kinds. These episodes acquaint us with the world around us — they tell us about the shapes, sizes, colours, and motions of objects, about the composition of our food, about the substances in the air, about the texture of things against our skin, about the condition of our bodies and our psychological well-being, and much more. We also have experiences of mental imagery, which seem like impoverished versions of regular experiences, detached from their normal causes.

It is a mark of conscious experience that we are, or can easily become, aware of having it. We can direct our attention inward (“introspect”) and think about the experiences we are having. We can recognize different experiences when we have them, compare them with other experiences, say whether or not we like them, and tell people about them.

We have strong preferences concerning our experiences and take efforts to cultivate some and avoid others. The nature of our experiences matters to us, and the nature of other people’s experiences should matter to us, too. All this is, I take it, uncontroversial.

We can define consciousness more precisely by making a contrast between conscious experiences and cases in which our senses pick up information without our being aware of it. Subliminal perception is an example. In a typical experiment, an image of, say, a camel or a camera is flashed before a person’s eyes for a fraction of a second followed by a “mask” — a second image that interferes with perception of the first. The person has no awareness of seeing the first image, but when asked to complete a word beginning with cam_____ they will probably say “camel” if the first image was a camel and “camera” if it was a camera, showing that a kind of perception had occurred.

The qualitative conception makes consciousness mysterious. How could brain processes create this subjective world of pure qualities, this qualia show? This is what David Chalmers calls the Hard Problem of consciousness.

A similar effect, called “blindsight”, occurs in some patients who have suffered damage to the visual processing areas of their brains, which leaves them blind in part of their visual field. Despite not being aware of seeing anything in the blind region, these patients can often accurately guess what is there, showing that their brains had received some visual information from the region.

Now, we can define consciousness as the common factor that normal experiences share and subliminal perception and blindsight lack. Scientists are currently working to devise experimental methods to pinpoint the brain systems involved in producing this common factor. The question for us is what this common factor is.

Here’s one view. Consciousness consists in the presence of mental qualities. To be conscious of features of the world — colours, sounds, tastes, textures, and so on — is to be aware of mental versions of them. Having a conscious visual experience of a ripe banana involves being aware of a mental yellowness, which is generated in us by yellow objects.

Similarly, experiencing something in one’s body (say, a pain in one’s toe) involves being aware of a mental quality produced by the bodily event. These mental qualities — qualia as they are sometimes called — are private and subjective, and they are presented to us in a specially direct way. Only you can experience your qualia, and none of us can be sure what another person’s qualia are like. (Maybe yellow things generate different qualia in each of us.) It’s as if there is a private show in our heads, our own private version of the world, which only we can witness.

In cases of subliminal perception and blindsight, by contrast, these mental qualities are absent. Our brains register some information about the features but do not produce the qualia that normally accompany it. I shall call this the qualitative conception of consciousness. The conception is widespread, at least among philosophers, and I take it that it is the one Kastrup, Strawson, and other critics of illusionism have in mind.

Now the qualitative conception makes consciousness mysterious. How could brain processes create this subjective world of pure qualities, this qualia show? This is what David Chalmers calls the Hard Problem of consciousness. And who is the audience for the show — who or what detects and reacts to the qualities? Is it other brain systems, or is it something distinct from the brain — a self or soul, perhaps?

Moreover, the view seals off consciousness into a private mental world, isolating it from the network of physical causes mapped by science. This in turn threatens to make consciousness ineffective, since there is good reason to think that all our reactions can be explained in terms of physical processes in the brain (at any rate, scientists haven’t found any that can’t). Defenders of the qualitative view may have to accept the counterintuitive conclusion that consciousness — even the feel of acute pain — has no effect on our behaviour. Such worries give us a reason to question the qualitative view of consciousness and look for an alternative.

Am I claiming that qualitative properties cannot exist, that they must be illusory? Kastrup thinks I am and attributes to me a “blatantly circular argument” for the claim, based on a passage in a recent article by me in Aeon magazine. But, as the paragraph following the one he cites makes clear, I am not making anything like so strong a claim. Of course, the fact that qualitative properties cannot be scientifically explained doesn’t prove that they are not real. There could well be things that science cannot explain. But it does give us a reason to explore the possibility that they aren’t real. After all, science has a good track record of explaining things that previously seemed deeply mysterious.

Illusionists reject the qualitative conception of consciousness. They hold that qualia, and the private show they constitute, are illusory; they seem to exist but don’t really. This is the core claim. (I have sometimes expressed this by saying that phenomenal consciousness is illusory — phenomenal consciousness being a form of consciousness consisting of qualitative properties.)

Illusionists reject the qualitative conception of consciousness. They hold that qualia, and the private show they constitute, are illusory; they seem to exist but don’t really.

Talking of illusions in this context is apt to provoke a strong reaction. Isn’t it circular to claim that consciousness involves an illusion? As Kastrup puts it, “illusions are experiential and therefore presuppose consciousness”. Despite this, I’m not going to back off. In fact, I’m going to double down. I believe that talk of illusion is highly appropriate here, and that Kastrup’s objection misses the mark. I’ll explain why in a moment, First, however, I need to sketch an alternative to the qualitative view of consciousness.

The alternative is that consciousness consists, not in awareness of private mental qualities, but in a certain relation to the public world — a relation that involves receiving information about things and reacting to them. For one to have a conscious experience of something is, I claim, for one to have a rich stream of sense-based information about it and for this information to have a wide range of effects — causing rapid behavioural responses, generating beliefs and desires, evoking memories, triggering associations, initiating emotional responses, and changing one’s psychological and behavioural dispositions in a myriad subtle ways. Episodes of blindsight and subliminal perception are not conscious, since the sensory information received is much more impoverished and does not have this wide range of effects.

We can draw this same distinction in terms of brain processes. Signals from the sense organs are routed to specialized processing systems, which are tuned up to recognize specific features, objects, and patterns. Some of this information has modest effects; it may guide rapid behavioural responses, but it is not stored in memory and doesn’t affect longer-term decision-making.

Other information, however, has much wider effects. Attentional mechanisms highlight features of interest and “globally broadcast” information about them to other brain systems, including ones for memory, reasoning, planning, language, emotional regulation, and motor control, generating the wide range of reactions and reactive dispositions I mentioned. It is this global broadcasting and its effects that constitute consciousness. Since all the states involved can be characterized in terms of the functions they perform within the brain, I shall call this the functional conception of consciousness.

I want to stress that I am not suggesting that these processes of information broadcast and reaction cause conscious experiences, as if consciousness were an extra thing, like an inner show. I am proposing that consciousness is this complex of informational and reactive processes. Similarly, when I talk of us having information about the world, I do not mean that we are something distinct from the brain states that carry the information. These states (scientists often call them representations) are not mental images which need to be observed and interpreted by a soul or self or boss brain system. They are just patterns of neuron firing, which are triggered by the presence of certain features in the environment and have appropriate effects on other brain systems. We are the human organisms partially constituted by these brain systems, and we are aware of the world in virtue of the internal effects these informational states have and the overall psychological and behavioural changes that result.

I am suggesting, then, that consciousness is a complex of informational and reactive processes. But that can’t be all, surely? I said that we can attend to our conscious experiences (introspect), compare them, and describe them. Doesn’t this mean that we are aware of mental qualities after all?

Not necessarily. In fact, the functional conception can easily be extended to explain this. On this view, experiences are physical states of the brain, and we can be aware of them in the same way we can be aware of anything else — namely, by receiving information about them and reacting to them. Introspection provides us with information about our experiences, enabling us to do the things I mentioned earlier — recognize our experiences, compare them, report them, say whether we like them, and so on.

At the level of the brain, this requires internal self-monitoring systems, which are sensitive to activity in our brains just as our sense organs are sensitive to things around us. But, as with awareness of the world, introspective awareness doesn’t involve or produce mental qualities; it simply is a cascade of informational and reactive processes. When we talk of what our experiences are like, we are referring, in an oblique way, to these effects and dispositions to react.

When we look at a ripe banana, complex representational and reactive processes occur in our brains. Our introspective systems monitor these processes but misrepresent them as a simple quality — the pure feel of yellowness.

Now we come to the bit about illusion. The reason we find the qualitative view so tempting is that introspection seems to present us with qualitative properties. Let me explain what I mean by this and why it’s not an incoherent or circular suggestion.

First, in speaking of illusion, I don’t mean that nothing is actually occurring. A lot is occurring — all the complex informational and reactive processes that constitute conscious experience. The illusion concerns the nature of these processes — the belief that they are simple qualia. When we look at a ripe banana, complex representational and reactive processes occur in our brains. Our introspective systems monitor these processes but misrepresent them as a simple quality — the pure feel of yellowness.

Second, I don’t mean to imply that introspection is faulty. Illusions can be useful. Think of the “desktop” on your computer, with its icons for files, folders, programs, and so on. (I have borrowed this example from Daniel Dennett’s book Consciousness Explained, which is a classic statement of the illusionist approach.) This is a sort of illusion — a highly simplified caricature of real data structures within the machine. But it is a highly useful illusion, which allows us to operate the machine without really understanding how it works. The same goes for the illusion of qualia. It is useful to have some awareness of our own experiences, so that we can tell others about them, for example. However, we don’t need to know all the fine details. A simplified caricature is all we need, and that what’s introspection provides.

But is the claim that qualia are illusory even coherent? Could we seem to have qualia without really having them? Kastrup thinks not. “Good Lord,” he exclaims, “the ‘seeming’ is already an experience in and of itself” [italics in original]. Does this simple point blow illusionism out of the water, as Kastrup supposes? There’s one way it might. Suppose that illusions involve awareness of mental qualities. That is, suppose that seeming to perceive a thing involves being aware of the mental qualities one would have been aware of if one were really perceiving it. Then, by analogy, seeming to introspect a mental quality would involve being aware of the mental quality one would have been aware of if one were really introspecting it. And that, presumably, is the very same mental quality. The illusion would involve a real instance of the thing that was supposed to be illusory! And if we were to say that this second instance of the quality is also illusory, then there would need to be a third one, and so on. On this view, clearly, the illusionist proposal is self-defeating or circular.

The flaw in this objection is obvious: it assumes that experience involves awareness of mental qualities. That is, it assumes the truth of the qualitative conception of consciousness. And that is the very point at issue. To be sure, if the qualitative conception were correct, then illusionism would be incoherent. But illusionists reject that conception in favour of the functional one. And the functional conception treats illusions differently.

According to the functional conception, seeming to perceive a thing involves undergoing the same informational and reactive processes one would have undergone if one really were perceiving it. Seeming to see a ripe banana involves having a stream of sensory information which produces the same psychological effects and dispositions that perception of a ripe banana would — evoking the same memories, triggering the same associations, initiating the same emotional responses, priming the same behavioural reactions, and so on. (It does not follow that one will actually act as if there is a banana there; one may know that one is the victim of an illusion, and resist. But the dispositions will persist at a basic level, tugging at one to act.)

Illusionists reject the view that consciousness consists in private mental qualities and argue that it involves being related to the world through a web of informational sensitivities and reactions.

Analogously, seeming to introspect a mental quality (say, the quale of yellowness) involves having a stream of introspective information which produces the same psychological effects that awareness of the actual quality would have done — producing appropriate beliefs, preferences, associations, emotional reactions, and so on. In short, to have the illusion of qualia is to be inclined to believe that one has them and to react as if one has them. This does not require the existence of the qualia themselves, so the account is not self-defeating or circular. (Some of the effects may be further experiences, perhaps of an emotional kind, but these can also be understood in the functional way.)

It is this emphasis on the effects of introspection that makes the notion of illusion so appropriate here. Think of the illusions created by stage magicians. By skilfully manipulating objects and misdirecting our attention, a magician aims to create a certain effect on their audience — to convince them that they have seen something out of this world. Introspection, illusionists claim, does something similar, producing a raft of psychological effects which leave us convinced that we are acquainted with a private world of mysterious mental qualities.

To sum up: Illusionists do not deny the existence of consciousness, but they do offer a different account of what consciousness is. They reject the view that it consists in private mental qualities and argue that it involves being related to the world through a web of informational sensitivities and reactions. They hold that mental qualities are a sort of illusion, and they respond to the objection that this claim is circular by pointing out that illusions can be understood in informational/reactive terms.

Of course, this does not establish that illusionism is true. All I have argued is that it is coherent. Kastrup may respond that, coherent or not, it is simply unbelievable — that we cannot doubt that mental qualities are real and quite different from informational/reactive processes, no matter how complex. (As he puts it, “the two domains are just incommensurable”.) I concede that it is hard to believe — I feel the pull of the qualitative conception myself. But I am not persuaded that we should trust our intuitive convictions here. After all, they may themselves be effects of an introspective illusion, and as we learn more about the brain processes involved in producing them, we may come to trust them less.

Daniel Dennett has suggested an analogy that might help: think of what happens if you tie a bucket of water to a rope and swing it around you in a circle. The water stays in the bucket. There seems to be a force keeping it there. People call it centrifugal force. This force is real, right? Can't you just feel it tugging at the rope? And can't you feel the same force pulling on you when your car corners too fast?

In fact, centrifugal force isn't real at all. There is no force pulling the water to the bottom of the bucket or you to the side of the car. The only relevant force is exerted by you pulling on the rope or the side of the car pushing on you. Centrifugal force is a powerful and well-understood illusion. This is a case where our intuitive convictions about what is real are completely wrong. Maybe our convictions about the reality of qualia are wrong, too.

At any rate, I believe that the illusionist approach is worth exploring and developing. It avoids the problems facing the qualitative conception and promises to demystify consciousness by showing how the human mind could be fully part of the physical world.

Kastrup accuses me of bad philosophical practice, speaking of “a smokescreen of conceptual obfuscation ... tortuous conceptual knots ... question-begging, sleights of hand ... perplexing webs of conceptual indirection ... layer upon layer of smoke and mirrors ... conjured-up artefacts of conceptual fog”. While I appreciate the analogies with stage magic, I hope I have done something to rebut this accusation and to explain what illusionists really believe.

Acknowledgement: The author is grateful to Daniel Dennett for his comments on an earlier draft of this article.