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Is Consciousness a “Controlled Brain Hallucination”? No.

Anil Seth explains away consciousness away using fashionable terms like that. As a pediatric neurosurgeon, I know from clinical experience that he is wrong

Philosopher David Chalmers famously divided the problem of understanding how consciousness is related to the brain by distinguishing between the easy and hard problems of consciousness.

The easy problem of consciousness is typically faced by working neuroscientists — i.e., what parts of the brain are metabolically active when we’re awake? What kinds of neurons are involved in memory? These problems are “easy” only in the sense that they are tractable. The neuroscience necessary to answer them is challenging but, with enough skill and perseverance, it can be done.

The hard problem of consciousness is another matter entirely. It is this: How can first-person subjective experience arise from brain matter? How do we get an ‘I’ from an ‘it’? Compared with the easy problem, the hard problem is, from the perspective of materialist neuroscience, intractable.

Many neuroscientists evade the hard problem by denying its relevance to neuroscience. In a recent essay, leading neuroscientist Anil Seth, co-director of the Sackler Centre for Consciousness Science at the University of Sussex in Brighton, eschews the easy/hard problem distinction:

[T]he rise of modern neuroscience has seen a more pragmatic approach gain ground: an approach that is guided by philosophy but doesn’t rely on philosophical research to provide the answers. Its key is to recognise that explaining why consciousness exists at all is not necessary in order to make progress in revealing its material basis – to start building explanatory bridges from the subjective and phenomenal to the objective and measurable… In my own research, a new picture is taking shape in which conscious experience is seen as deeply grounded in how brains and bodies work together to maintain physiological integrity – to stay alive. In this story, we are conscious ‘beast-machines’, and I hope to show you why.

Anil Seth, “The real problem” at Aeon (November 2, 2016)

So how is it that we “conscious ‘beast machines’” are conscious? Seth:

To answer this, we can appeal to the same process that underlies other forms of perception. The brain makes its ‘best guess’, based on its prior beliefs or expectations, and the available sensory data. In this case, the relevant sensory data include signals specific to the body, as well as the classic senses such as vision and touch. These bodily senses include proprioception, which signals the body’s configuration in space, and interoception, which involves a raft of inputs that convey information from inside the body, such as blood pressure, gastric tension, heartbeat and so on. The experience of embodied selfhood depends on predictions about body-related causes of sensory signals across interoceptive and proprioceptive channels, as well as across the classic senses. Our experiences of being and having a body are ‘controlled hallucinations’ of a very distinctive kind.

Anil Seth, “The real problem” at Aeon (November 2, 2016)

There’s a lot more to Seth’s rather verbose essay, but the essence of his theory of consciousness is that the brain integrates a cacophony of sensory inputs to fabricate an explanation for perceived reality — a “controlled hallucination” — that we call consciousness. This view, that consciousness is, in one sense or another, the consequence of massive parallel processing going on in neural circuits in the brain, is common among modern neuroscientists. But it can’t be true.

To see why, consider the neurological consequences of split brain surgery and the congenital brain condition called hydranencephaly.

In split brain surgery, neurosurgeons cut the massive bundle of nerve fibers connecting the cerebral hemispheres in order to lessen the propagation of seizures in patients with epilepsy. The two brain hemispheres are disconnected — information from one hemisphere cannot readily be transmitted to the other. This radical disconnection of the brain hemispheres causes massive interference with “sensory signals across interoceptive and proprioceptive channels, as well as across the classic senses” but, contrary to what Seth’s theory seems to predict, there is no impairment of consciousness whatsoever. Patients with split brains (I have performed the surgery myself) have very subtle perceptual disabilities of which they are almost always unaware, and there is no impairment in consciousness.

Neuroscientist Yair Pinto calls this split brain state “divided perception but undivided consciousness”. It is difficult to reconcile Seth’s notion of consciousness as “controlled hallucination” as a result of massively integrated perceptions with the full preservation of consciousness following cutting the brain hemispheres in half. Consciousness is not, in this circumstance, subject to the scalpel, as Seth’s materialist theory implies it must be.

An even more intractable problem for Seth’s “controlled hallucination” theory is hydranencephaly. Hydranencephaly is a condition in which children are often born without brain hemispheres. The cause is usually a massive intrauterine stroke that destroys all of the brain above the brainstem. Nearly all of the perceptual circuits on which Seth’s theory depends are not merely cut, but are completely destroyed, yet children with hydranencephaly are fully conscious.

I have cared for these children myself (I am a pediatric neurosurgeon). Although they are quite handicapped, they are certainly conscious, interactive, and show a full range of emotions — laughter, crying, glee, fear, and such. Complete destruction of the cerebral hemispheres is fully compatible with consciousness.

Seth’s theory that consciousness is a “controlled hallucination” occasioned by integration of massive sensory inputs by the brain hemispheres falls apart when we consider that disconnection of the hemispheres — and even destruction of the brain hemispheres — is compatible with full consciousness (despite profound sensory and motor disabilities). Only a dualist or idealist understanding of the mind–brain relationship can survive the evidence provided by split brain research and routine clinical experience with children with hydranencephaly.

The only “controlled hallucination” here is the belief that materialism can explain the mind.

Note: Jaxon Buell (2014–2020) died at five years of age due to complications from his condition (80% of his brain missing). “Jaxon was unable to walk or talk, but his parents shared his many milestones on the now-deleted Facebook page We Are Jaxon Strong, where followers saw him smiling and appearing to communicate with noises and eye contact.” – People (April 7, 2020)

You may also wish to read: Philosopher: I’m neither me, myself nor I… Yet I give interviews! Theoretical philosopher Thomas Metzinger tells his interviewer “Nobody ever had or was a self. Selves are not part of reality.” If Metzinger is an evanescent process without substantial enduring reality, does he refuse to pick up his paycheck? How real is “not part of reality” here? (Michael Egnor)


Michael Egnor

Senior Fellow, Center for Natural & Artificial Intelligence
Michael R. Egnor, MD, is a Professor of Neurosurgery and Pediatrics at State University of New York, Stony Brook, has served as the Director of Pediatric Neurosurgery, and award-winning brain surgeon. He was named one of New York’s best doctors by the New York Magazine in 2005. He received his medical education at Columbia University College of Physicians and Surgeons and completed his residency at Jackson Memorial Hospital. His research on hydrocephalus has been published in journals including Journal of Neurosurgery, Pediatrics, and Cerebrospinal Fluid Research. He is on the Scientific Advisory Board of the Hydrocephalus Association in the United States and has lectured extensively throughout the United States and Europe.

Is Consciousness a “Controlled Brain Hallucination”? No.