From Order to Possibility: A New Theory of Consciousness
What “The Entropic Brain – Revisited” reveals about consciousness and psychedelics
https://www.sciencedirect.com/science/article/abs/pii/S0028390818301175?via%3Dihub
What if the difference between ordinary consciousness and extraordinary experience isn’t what you see—but how constrained your brain is?
That’s the central question behind The Entropic Brain – Revisited, a follow-up to one of the most influential modern theories of consciousness.
The idea is simple, but powerful:
The richness of your conscious experience depends on how flexible—or constrained—your brain activity is.
And psychedelics, according to this theory, temporarily loosen those constraints.
The Core Idea: Consciousness Has an “Entropy Level”
In physics and information theory, entropy refers to uncertainty or variability.
Applied to the brain, it means:
Low entropy → stable, predictable brain activity
High entropy → flexible, variable, less constrained activity
The paper argues that:
The “richness” of conscious experience tracks the entropy of brain activity
So when brain activity becomes more diverse and less predictable, experience becomes:
More vivid
More associative
More emotionally and perceptually complex
Psychedelics Push the Brain Toward Higher Entropy
One of the strongest claims—now backed by multiple studies—is that psychedelics reliably increase brain entropy.
This means:
Brain networks become less rigid
Communication patterns diversify
The system becomes more sensitive to internal and external inputs
In practical terms:
The brain becomes more open, but also less stable
This helps explain common psychedelic experiences:
Novel thoughts and insights
Emotional breakthroughs
Unusual perceptions or connections
The Sweet Spot: Not Too Rigid, Not Too Chaotic
A key refinement in this “revisited” version of the theory is that more entropy isn’t always better.
There are limits.
Too little entropy → rigid thinking (e.g., depression, compulsive loops)
Too much entropy → disorganization or even loss of consciousness
The brain operates best near a balance point often called “criticality”:
A state where the system is maximally flexible but still coherent
Psychedelics may temporarily push the brain closer to this critical zone.
Why “Set and Setting” Matter (Scientifically)
One of the most interesting updates in this paper is how it explains something long known in psychedelic culture:
Set and setting matter.
The theory provides a mechanism:
In high-entropy states, the brain becomes more sensitive to influence
External environment and internal mindset shape the experience more strongly
So instead of being a vague idea, this becomes a predictable property of brain dynamics.
Consciousness, Measured
Another advancement in this paper is the attempt to quantify consciousness more precisely.
Researchers now use measures like:
Lempel-Ziv complexity
EEG/MEG signal diversity
These metrics can:
Distinguish waking from unconscious states
Track changes in altered states
Potentially map subjective experience to brain activity
This is a major step toward bridging the gap between:
Brain activity
Subjective experience
Clinical Implications: Why This Matters for Mental Health
The theory isn’t just abstract—it has practical implications.
Many mental health disorders involve overly rigid brain patterns, such as:
Depression → repetitive negative thinking
Addiction → fixed behavioral loops
OCD → inflexible cognitive patterns
By increasing entropy, psychedelics may:
Temporarily disrupt these rigid patterns, allowing new ones to form
This could explain why:
A few sessions can produce lasting changes
Patients report “reset” experiences
The paper also suggests potential applications in:
Disorders of consciousness (e.g., coma, vegetative states)
Neurological conditions where brain activity is too constrained
The Role of Serotonin
Another important update connects the theory to serotonin.
Recent findings suggest serotonin may encode:
Uncertainty or “surprise” signals, rather than simple reward
This fits neatly with the entropic brain model:
Psychedelics act on serotonin systems
This increases uncertainty → increases entropy → alters consciousness
The Bigger Picture
What makes this paper important is not just its findings—but its ambition.
It tries to answer one of the hardest questions in science:
How do physical brain processes relate to subjective experience?
By using entropy as a bridge, the theory suggests:
Brain activity and experience are two sides of the same process
More complex brain dynamics = richer experience
Final Take
The Entropic Brain – Revisited doesn’t claim to solve consciousness.
But it offers something rare:
A framework that connects:
Brain activity
Subjective experience
Mental health
Into a single model.
And its core insight is deceptively simple:
Consciousness isn’t just about what your brain is doing—
it’s about how constrained or flexible those processes are.
Robin L. Carhart-Harris, The entropic brain - revisited, Neuropharmacology, Volume 142, 2018, Pages 167-178, ISSN 0028-3908,