Before we fall directly down the rabbithole (wormhole?) of galactic-scale minds (yes, really) we have to first consider the mainstream. While philosophers continue to debate the nature of the human soul, modern neuroscience has been busy. It has developed an extremely robust, sophisticated model to explain why psychedelics feel so incredibly profound. It achieves this without needing to abandon the conception of the brain as simply a biological machine. To the materialist, psychedelics do not open a portal to another dimension or remove the scales from your eyes; they simply crash the system.
The current theory is called “Predictive Processing.” This model suggests that what we witness as the world around us is, in fact, a powerful hallucination that the brain is constantly updating and optimising. Let’s put it simply:
The brain is locked inside the skull with no direct access to the external world. All it receives are chaotic electrical signals from the eyes, ears, skin, etc. To make sense of all this chaos, the brain does not simply record reality, like a camera. Instead, it maintains a constantly updating internal model of the world. This amounts to a best guess as to what should be out there, as opposed to what actually is. This means it needs only pay attention to sensory data when something contradicts its prediction – for example, a spider running up your arm.
This is, of course, a survival mechanism. Processing the sheer volume of data contained in raw perception in real-time would be incredibly slow and chemically challenging. Hallucinating a predictable world is much faster. Therefore, we live in a “controlled hallucination”, designed to keep us alive, rather than show us the truth of reality.
So, what happens when we introduce a psychedelic compound into this system?
The leading explanation comes from Dr Robin Carhart-Harris, of Imperial College London. He proposed the REBUS Model (Relaxed Beliefs Under Psychedelics). Harris argues that psychedelics chemically dismantle the brain’s top-down hierarchy. This weakens the day-to-day hallucination, removing all the associations and expectations connected to various aspects of the outside world. “This is a table”, for example, contains so, so, so many elements. As does “I am a separate self”.
When these elements of perception begin to disintegrate, the brain can no longer filter out the raw noise of existence. Suddenly, the floodgates open. Overwhelming sensory data, no guardrails or prior knowledge. The walls may begin to “breathe” because the brain no longer has an inbuilt prediction of what a wall is, whether it is static, whether it is even solid. The commonly reported feeling of oneness with the universe is not a rediscovered connection to some giant cosmic consciousness. Rather, the specific neural network responsible for the hallucination of “self” has simply been taken offline.
To the materialist, then, this profound, transcendent, revelatory space psychedelics allow us to enter is just another delusion. Beautiful perhaps, but a simple glitch nonetheless. The brain, stripped of its ability to predict, enters a state of plasticity (this is exactly why psychedelics are so potentially exciting in a therapeutic context).
This argument is pretty compelling because it is grounded in observable data. It explains the visual distortions, the dissolution of the ego, and the powerful emotions involved in perceiving “spirits” or alternate dimensions. In this view, while psychedelic effects are neatly explained away, the “Hard Problem” is far from solved.
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