The Mechanism — The Lock, Not the Room

There is a man I cannot think about without my eyes going. He showed me where the door was, and what to do once I was through it — and everything in this post — the default mode network, REBUS, the receptor binding, the models with acronyms — is an attempt to describe what was happening in those rooms.

I want to say at the outset that the attempt falls short of the first sentence.

That is not a complaint about science. It is the finding. We are going to go a long way into the machinery, further than this series has gone before, and the machinery of the default mode network is real and beautifully worked out. And then we are going to arrive at the place where the instruments stop, which turns out to be exactly where he was standing.

For a similar story but one that you can see or hear click below or read on.

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The Default Mode Network Thinks About You

Here is what neuroscience found, and it deserves to be stated at full strength before anything is asked of it.

There is a set of brain regions that become more active when you are doing nothing in particular. That was the surprise. For decades imaging studies were built around tasks — solve this, watch that, press the button — and the resting periods between tasks were treated as the baseline, the nothing, the part you subtract. Then somebody looked at the nothing.

The nothing was busy. A distributed system running through the medial prefrontal cortex and the posterior cingulate lights up the moment you stop attending to the world, and quiets when you go back to it. They called it the default mode network, because it is what the brain defaults to.

And what the default mode network does, more than anything else, is maintain a person.

What it does, as far as anyone can tell, is you. Autobiography. Rehearsal of conversations that have not happened. Editing of conversations that have. The running assessment of how you are doing, how you are being seen, and what that means about you. The narrative self, maintained continuously in the background, for free, whether or not you asked for it. Well maybe it’s not for free?

Then two findings arrived from opposite directions.

One lock — the default mode network — and two keys. This is the point at which most writing on the subject declares the matter settled and goes home.

What the Model Actually Says

But there is a more interesting version, and it is more interesting because it explains rather than correlates.

The dominant model is called REBUS — relaxed beliefs under psychedelics — proposed by Robin Carhart-Harris and Karl Friston. It sits on top of predictive processing, which holds that perception is not a camera. The brain is running a model of the world and constantly predicting what should arrive next; what reaches you as experience is that prediction, corrected by whatever the senses insist on. The predictions are called priors, and they are built from everything that has ever happened to you.

Priors are why you can read a word when all the letters are mxudiep. They are why you can walk through your own house in the dark. They are also why you cannot stop hearing a certain tone of voice as contempt, forty years after you learned to.

What REBUS proposes is that psychedelics do not add anything. REBUS says they relax the priors. The high-level models loosen their grip, sensory information stops being so heavily filtered, and what comes through has not been pre-shaped as thoroughly as usual.

Now I have to declare an interest, because this is where the model and my own notation collide.

Long before I had read any of this, the standard on this site for describing experience has been ⟨v(t)⟩ = ⟨ψ(t)| V̂ |ψ(t)⟩ — where V̂ is the valence operator, the lens. Habits, beliefs, emotional patterns, the accumulated apparatus through which raw existence becomes your experience of it. And ⟨v(t)⟩ is what is actually felt.

I did not build that notation from neuroscience. I built it to describe something I had sat with. But REBUS is a description of V̂ loosening, and the two are saying the same thing in different alphabets.

And they are not the first two. Aldous Huxley, writing in 1954 after taking mescaline, borrowed an idea from Bergson and called the brain a reducing valve — arguing that what we call perception is mostly elimination, the nervous system keeping out the overwhelming majority of what could be known so that a human being can get through the day. Priors, veils, valve. Three vocabularies for one claim, and the Buddhist one is by some centuries the oldest.

And there is an older word for the same thing. My own tradition calls them veils klehas— obscurations, adventitious in the technical sense: arrived rather than intrinsic, and therefore removable. Priors and veils are one object under two vocabularies. I did not build that notation from neuroscience. I built it to describe something I had sat with. But REBUS is a description of V̂ loosening under exactly these conditions, and the two are saying the same thing in different alphabets. Make of that what you will. I find it hard to ignore.

Your Cosmology Is One of the Veils

Which brings us to what I think is the most useful idea in this entire series.

If experience is raw signal shaped by priors, and priors are built from everything that ever happened to you, then a great many of your priors were not built by you at all. They were installed. Your language. Your assumptions about what exists. What a vision is, what it would mean, and who might be sending it.

Your cosmology is a prior. Not a belief sitting on top of your priors — one of them. Which is to say: one of the veils, and not the thinnest.

And priors relax. Priors do not vanish.

Look at what that predicts. Take the same machinery, in the same species, loosened the same way — and put it in a sixth-century-BCE Judahite priest, a fourth-century Egyptian mystic, and a Tibetan yogi. The relaxation is common. What is left to shape the content is not. So the priest gets a throne, a chariot, wheels and a glory that fills a temple, because those are the highest things his tradition has.

The Egyptian gets doors opening in the disk of the sun and seven Fates with the faces of asps. The yogi gets deity, mandala, luminosity — because that is the vocabulary his lineage handed him. And a merchant in a cave above Mecca, with no visionary tradition prepared for him at all, gets a very rough time indeed, and comes down the mountain shaking and asking to be covered.

Same door. Different architecture, because the architecture is what survives the loosening. The same uncovering gives you a throne in Judah, a mandala in Tibet, and a very rough night in a cave above Mecca.

And there is a detail that supports it, which I wrote down in an earlier post without understanding what I was looking at. Ezekiel’s report is full of hedging — the likeness of, as the appearance of, as it were, like unto the colour of. I read that as scrupulous honesty, and it is. But it is also a man whose priors have nothing prepared for this. He is reaching for the nearest available object and rejecting it, over and over, in public.

There is one more thing that fits, and it comes from the modern reports rather than the ancient ones.

People describe the world going fluid. Surfaces breathing. Edges refusing to hold still. Things flowing into one another that are supposed to stay separate.

That is not a poetic flourish for the experience. It is the mechanism of the default mode network and its priors, seen from inside. What makes the world feel solid is the prior — the priors asserting, with enormous confidence, that this edge is an edge and will still be there in a second. Loosen the confidence and solidity is the first thing to go. Water is simply the closest thing in ordinary life to what perception feels like when it stops insisting.

Vocabulary Follows Repeatability

I said in an earlier post that the prophets got poetry and the yogis got technical manuals. I want to correct that, because it was too neat, and the correction is more interesting than the claim.

The prophets’ successors got manuals too.

Look at what grew out of Enoch. Not one vision but a library, developing across centuries — and at the end of it the Hekhalot literature, the Books of Palaces. That material has a technical name for the practice, yeridah la-merkavah, the descent to the chariot, counterintuitively “down” ( Alice would love this part) for what is plainly an ascent. It has seven palaces with named guardians and passwords. It has preparation protocols. And it has something no poem ever needs: error correction. At the sixth palace, the texts warn, you will seem to see water. You must not say water, water. A specific perceptual trap, taught in advance, so that you will recognise it when it happens to you.

You do not write that sentence after one experience. You write it after enough people have made the same mistake in the same place that it becomes worth warning about.

The same pattern turns up wherever the going was repeatable. Sufism produced a whole taxonomy of maqāmāt and aḥwāl — stations you attain and hold, states that arrive and pass. The Abhidharma enumerates mental factors with the patience of a botanist and distinguishes stages of absorption from one another. And in the West, Plotinus built a real vocabulary — henōsis, union; ekstasis, standing outside; aphairesis, the stripping away; epistrophē, the turning back toward the source.

Then Porphyry, his student, does something that stops me every time. Editing his teacher’s works, he records that Plotinus reached union four times in the years they were together — and that he himself, Porphyry, managed it once, at the age of sixty-eight.

He is keeping score. In the third century, a student is counting his master’s attainments and measuring his own against them, and writing the number down.

🏛️  “Never did eye see the sun unless it had first become sun-like, and never can the soul have vision of the First Beauty unless itself be beautiful.”

— Porphyry, Life of Plotinus 23

That is not devotional literature. That is a field report.

So the difference between the traditions was never intelligence, and it was never the capacity of the language. Sanskrit is not magic. What made the difference is whether people could get back to the same place repeatedly and compare notes — because vocabulary follows repeatability. One encounter gives you the best poetry a person can write. A method gives you a manual, and a manual gives you the sixth palace and the water.

And that reframes everything this series has documented. When a transmission was broken, the loss was not only the practice. It was the language for talking about it — and once the transmission goes, the next person who gets there has no way to say what happened, and nobody to say it to.

The Valve, and Who Said It First

Huxley got here in 1954, and he was borrowing from Bergson. The idea in The Doors of Perception is that Mind at Large is available to every one of us, and that the brain and the nervous system are eliminative rather than productive — their job is to keep out the overwhelming majority of what we could otherwise know, so that a person can get through an ordinary Tuesday. He called it the reducing valve.

Bergson, priors, veils, valve. Four vocabularies and one claim, and the oldest of them is the Buddhist one. None of them describes a faculty being switched on. All four describe something being taken away.

Where the Default Mode Network Story Stops

Now the honesty, and I am going to be harder on this material than most people writing about it are.

Start with the strongest case, because it is genuinely strong. Depression — specifically the ruminative kind, the loop that will not release, the same three thoughts about yourself running all night — shows up in this research repeatedly. Rumination correlates with heightened activity and connectivity in exactly this network. Which makes a terrible kind of sense: if the default mode network is the system that narrates you to yourself, then depression looks like the default mode network stuck in a groove, playing one track. And in trials, people given psilocybin under supervision for treatment-resistant depression have reported the loop breaking.

So yes — the default mode network runs your self-narrative, and the illness that is a self-narrative gone wrong meets it in the same place. That is not nothing.

But I would not go further than that, and the version of this you will hear elsewhere goes much further.

Not all mental illness lives here. The default mode network is implicated in rumination, and in some anxiety and addiction findings, and it is one part of a much larger picture in conditions like psychosis and PTSD, where quite different systems are doing the heavy lifting. And correlation is doing a great deal of work in these sentences: a depressed brain shows altered connectivity, and nobody can yet tell you whether that is the illness, a consequence of the illness, or simply the shape of thinking about it.

Then the models themselves. The entropic brain is a hypothesis. REBUS is a model — an elegant one, well motivated, and not a demonstrated fact. REBUS explains beautifully and proves nothing. The default mode network as ego is a simplification, and its own authors hedge it considerably more than the people quoting them do. Psychedelic neuroimaging is a young field with small samples, difficult blinding — it is not easy to give someone a placebo they mistake for a high dose — and it carries all the replication troubles the rest of psychology has been reckoning with. Several results reported with great confidence have since become more complicated.

I am not saying the science is bad. I am saying it is science: provisional, contested, and being argued about right now by the people best qualified to argue about it. If I presented it to you as settled, I would be doing the thing this entire series exists to warn about.

And even if every finding held perfectly, there is a limit built into the method that no amount of resolution will fix.

A scan can tell you that the default mode network decoupled. It can tell you how far, and for how long, and how well that tracked what the person said afterwards. What it cannot tell you is whether they took a wrong turn. It has no reading for that was the sixth palace and you should not have spoken. It has no reading that separates ego dissolution from a person simply coming apart, because from the outside those look identical, and it is measuring the outside.

I ended the last post by saying the residue will tell you what was in the cup and never what the cup was for.

Beyond the Default Mode Network: The Only Instrument There Has Ever Been

So what does work? The answer this series keeps arriving at is transmission.

There is exactly one instrument for the inside of a mind, and it is another mind that has been there.

You come back, and you describe what happened as best your language allows, and somebody who has stood in that place tells you yes, that, keep going. Or no — that is not what you think it is, do not follow it. Or stop, come back, you are not ready for this yet.

That is not pastoral care. It is calibration, in the strict sense: comparison against a reference. It is what transmission is for. And the reference has to be a person, because there has never been anything else to compare against.

The Talmud keeps a record of what happens without it. Four entered the orchard. One died. One went mad. One apostatised. And Rabbi Akiva entered in peace and departed in peace — a phrase doing precise technical work, marking the single member of the party who could go and return intact. That is not a moral judgement about the other three. It is a report on outcomes.

There is one more thing about ego dissolution, and it is the reason all of this converges.

The default mode network is not only the self network. The default mode network is heavily involved in social cognition — modelling other minds, taking another’s perspective, maintaining the line between what is you and what is someone else. Which means that ego dissolution and the dissolving of the boundary between self and other are not two separate effects. They are one effect, in one system.

The Scaffolding Is Built to Come Down

One question is left, and it has been sitting under this whole series. Why did this transmission survive when so many did not?

Not because it was left alone. That answer is available and it is false. Buddhism was driven out of India, its own homeland — Nalanda destroyed around 1193, and within a century the tradition was effectively gone from the country that produced it. In China, the persecution of 845 forcibly returned a quarter of a million monks and nuns to lay life. In Tibet itself the transmission genuinely broke in the ninth century, under Langdarma, and the lineages had to be brought back in from India afterwards — Tibetans call it the later diffusion, which is a polite name for starting again. And then 1959.

So, three things instead.

It walks. A transmission carried in people rather than buildings survives the loss of buildings. In February 1959 the sixteenth Karmapa left Tsurphu with a hundred and sixty monks, lamas and lay people, and twenty-one days later they came down into Bhutan with the statues, the thangkas, the reliquaries and the texts of the lineage. Nineteen years earlier, at sixteen, he had written four lines saying that his people would not stay, that they would go to India, and that the cuckoo knows when to go. You cannot confiscate that at a border and you cannot burn it. It leaves on foot.

There is no apex. This tradition is not flat — it is steeply hierarchical, full of ranks and thrones and seniority. But there are four major schools and no single office above them, no council that can declare a thing heretical for everyone at once (although they have tried). That is not flatness. It is redundancy. One hierarchy is one decapitation from over. A dozen parallel ones are not.

And the third one is the answer. In this tradition, direct unmediated experience is not a threat to the institution. It is the product. There is nothing for the institution to protect, because the entire purpose of the apparatus is to hand you the thing itself.

Hold that against what happened in Europe. Marguerite Porete was burned in 1310. Eckhart was condemned in 1329. Not for being wrong — for being unnecessary. If a person can reach God without the sacrament, the sacrament becomes optional, and an institution whose position depends on being the way through cannot afford people who found another way. The mystics kept being disciplined by their own church because, structurally, they were competition.

An institution whose success condition is producing people who no longer need it cannot be threatened by them.

And this one tells you so, in who it chose as its hero. Not an abbot. Not a throne-holder. A murderer who became a yogi, lived in caves, wore a cotton sheet in the snow, sang, and held no position of any kind. When a tradition puts Milarepa at the centre, it has told you exactly what it is for.

Which brings me back to a man I cannot think about without my eyes going.

He had the map, and the key, and he had been in the room himself — and that is the wrong way to say it, because the lama is not the guide to the room. He is the room. That is what the dissolution is.

Two technologies, then. One works with a molecule and one works without. Both are subtraction. And the room is built together with the lama so that you can eventually be it yourself.

QP

Further Reading:

On this site:

1. Empty First — fasting as a complete technology with no molecule in it. →

2. The Recipe You’d Die For — Dioscorides, and wine as the vehicle of the ancient world. →

3. Pharmakon — process over plant. →

4. The Purity Law — the first drug law, and legislating what may be in a cup. →

5. To Die Before You Die — rehearsal for death. →

6. Divine Madness — ego-death as metamorphosis rather than annihilation. →

7. Set and Setting — the container, and the prophets who engineered it. →

8. The Mithras Liturgy — the one manual that survived, and is useless. →

9. The Villa Vesuvio Apotheke — the evidence sitting unscraped on a shelf. →

10. They Lost the Ingredients — soma, and the only tradition that filed the paperwork. →

11. The Two That Survived — iboga and ayahuasca, and why. →

12. The Mechanism — the neuroscience, and where the instruments stop. →

The science, free and in full

• David E. Nichols, “Psychedelics”, Pharmacological Reviews 68(2), 2016

• Carhart-Harris & Friston, “REBUS and the Anarchic Brain”, Pharmacological Reviews 71(3), 2019

The older manuals:

• Hagigah 14b — the four who entered the orchard →

• Porphyry, Life of Plotinus →