Is your sense of reality in fact a hallucination?

For well over 2,000 years, humans have been puzzled by the nature of consciousness. Is there a little nerve centre in your brain - a “mini-you” directing affairs - which one day science will be able to locate? Or is there a stranger reason for your sense of self?

"Whether there will be a satisfying explanation of consciousness in my lifetime I honestly don't know," cognitive scientist Anil Seth tells The Irish Times. But the author of Being You - an acclaimed analysis of our current state of knowledge - does not accept we are as mystified as our ancestors. "This is just rubbish, we know a lot more than we did."

Outside of the American philosopher Daniel Dennett, the Englishman Seth is probably the closest thing to a celebrity in consciousness studies today. His big idea is that consciousness is a "controlled hallucination".

"It's not my term", he acknowledges, and nor is he claiming any special knowledge. Rather he is determined to communicate where the most fruitful avenues of investigation lie. His Ted Talk on the subject - which includes the memorable claim that "when we agree about our hallucinations that's what we call reality" - has over 12 million views.

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“I have zero sympathy with mysterianism - the idea that we’re just not smart enough understand consciousness. This may be true but you don’t just give up.

“The beautiful thing about science is that it doesn’t depend on how smart an individual is. It depends on how smart the whole process is. I think it’s unwise to put limits on what we might come to understand over time.”

Seth discusses further as this week’s Unthinkable guest.

If consciousness is a "controlled hallucination" who is doing the controlling?

Anil Seth: "It's not like you - as the essence of you, some sort of immaterial self - that's pulling the strings to control the hallucination. It's the world doing the controlling, really. The sensory signals that come into your eyes and ears - they are keeping your perceptions attuned to reality.

“In a sense, you are doing the controlling too because we - as the organism - perform actions all the time and those actions also bring our perceptual ‘best guesses’ into register with the world… but all of this goes on under the hood.

“So it’s not like the conscious ‘you’ that’s thinking of what you’re having for dinner that is controlling the hallucination - no, no, no - this is all just the wiring of your brain doing what it does.”

By describing reality as an agreed hallucination are you playing into the hands of those who might like to believe, for political or other reasons, that reality, or truth, is all relative?

"I would hope it would rather do the opposite… It allows us to appreciate that other people might see the same situation slightly differently and I think that's a necessary precondition for dialogue and for understanding.

“A good example of that is the phenomenon of the dress… that half the world sees as blue and black and the other half sees as white and gold. It brings to the surface something that probably goes on all the time that is hidden because it’s not that dramatic.

“If you and I were together and we looked out a window and there was a red car across the street we will both say, ‘the car is red’. It’s easy to assume you’re having the same experience as me but we’re probably not, we’re probably having a slightly different experience of the same situation.

“It’s not that the real world doesn’t exist, it’s not a hallucination in that sense. Things exist. The world is real. It is the way it appears to us in our experience that’s a construction.”

Does the science imply we should be more tolerant of one another because of this?

"I think like most science it depends how to read it and how you take it. The science itself doesn't have a moral character but there is an opportunity here to do exactly that - to induce tolerance… to accept people will have different perceptual experiences…

“Of course, it [the science] can also do the opposite. It can licence a kind of solipsism or nihilism where people say, ‘I don’t care; I see things the way I see them and that’s enough for me’.”

You suggest a better understanding of consciousness will help in the treatment of mental health problems. How so?

"It's still early days but there are a few examples where I think we see some progress. One is in conditions like schizophrenia, psychosis, another is in the area of hallucinations as they are described in the medical literature.

“We can now get a grip on this by thinking about disturbances to the process of normal perception - where our brain’s predictions, our brain’s best guesses, become untethered from their causes in the world… Even just knowing what’s going on can be quite therapeutic and beneficial.”

Philosophers and neuroscientists have often clashed on this topic. Can they be reconciled?

"There has been a happier marriage than there was…. Phenomenology is for me very important - that's a branch of philosophy that's no so much about understanding the mind-brain relationship but characterising experience.

“If we are trying to develop a science of consciousness it’s not enough to say ‘consciousness is what goes away under general anesthesia’ - that’s a starting point. We need to understand the explanatory goal. We want to understand what experiences are like, and phenomenology is very rich here.”

In the absence of scientific certainty, there are lots of different theories about where consciousness comes from (see Where are 'you'?, below). What do you make of panpsychism, for example, the idea that consciousness is everywhere in the natural world?

"Theories inhabit different levels. The sorts of theories that I engage with more are all broadly materialistic, which means they see consciousness as identical to, emergent from, or intimately related to, what's going on in the brain and the body.

“Then you’ve got the philosophical - in quotation - theories - they are more metaphysical positions… something like panpsychism, which says consciousness is fundamental and ubiquitous.

“To me, it’s like an easy ‘out’ to the hard problem: Consciousness seems really mysterious… so let’s just say it’s everywhere. Problem solved! Except it doesn’t explain anything. It’s not testable. Yeah, I think it’s a form of magical thinking.”

Where are ‘you’?

Today there are a few chief suspects, of varying credibility, for the seat of consciousness:

1. In your soul: A comforting thought - who wouldn't want an immaterial, immortal spirit? - but science is not on your side.

2. In your brain: Okay but where exactly? Few scientists believe the kind of consciousness we have can be reproduced by a brain in a vat. "In practice, all the time, all our conscious experiences are deeply shaped by the body, " says Anil Seth.

3. In the 'spread mind': A theory linked to charismatic psychologist Riccardo Manzotti, which says consciousness is "spread" between you and perceived external objects - making you literally at one with the world.

4. Everywhere: Panpsychism decrees that consciousness doesn't pop into existence but is rather "already there" - in rocks and trees and molecules and people. Neurophilosopher Patricia Churchland has likened the theory to belief in "pixie dust" and leprechauns.

5. At your cerebral workspace: Daniel Dennett says we tend to think of consciousness as an internal movie but it's more like "fame in the brain". This captures the idea of consciousness as influence, or clout, that emerges over brain states. Other cognitive scientists talk of mental content "becoming conscious" when certain conditions are met within the working brain.

The research is still young and Seth warns against any "immediately satisfying" theory. "It's like gobbling a bag of crisps before dinner; it might feel nice but it's not going to help".

Being You: A New Science of Consciousness by Anil Seth is published by Faber