The Invisible Membrane Between You and Everything Else

Formative Note

This essay represents early thinking by Ryan Collison that contributed to the development of A Theory of Meaning (AToM). The canonical statement of AToM is defined here.

Where do you end and the world begin?

It seems like an easy question. Your skin, obviously. The boundary is right there—visible, tangible, the surface where self meets not-self.

But the deeper you look, the stranger this boundary becomes. Your lungs are inside you, but the air passing through them is outside you—until it crosses some invisible threshold and becomes part of you, then crosses back and becomes world again. Your gut contains trillions of bacteria that aren't genetically you, but without them you'd die. Your brain receives signals from a world it can never directly touch, constructing reality from patterns that cross the divide.

The boundary between you and everything else is not a wall. It's a membrane—a selective interface that determines what flows in, what flows out, and how the inside remains organized despite the chaos outside.

This membrane has a name. It's called the Markov blanket. And understanding it may be the key to understanding what it means to be a self at all.

The Statistical Self

A Markov blanket is a concept from probability theory, but don't let that scare you. The idea is intuitive once you see it.

Imagine a system—any system—surrounded by other things. The Markov blanket is the set of variables that separates the system's internal states from everything external. If you know the blanket states, you know everything there is to know about the statistical relationship between inside and outside. The blanket screens off the interior from the exterior.

For a cell, the blanket is roughly the cell membrane plus the receptors and channels that span it. The membrane determines what molecules enter and exit. It's the interface between cellular inside and environmental outside.

For you, the blanket is more complex. It includes your sensory surfaces—everything that receives signals from the world. Eyes, ears, skin, tongue, nose, the interoceptive sensors monitoring your organs. It also includes your active surfaces—everything that acts on the world. Muscles, vocal cords, glands, the movements that change your relationship to the environment.

Sensory states flow in. Active states flow out. Internal states—your beliefs, your models, your predictions—live behind the blanket, forever insulated from direct contact with reality.

This is the statistical self: the pattern of internal states that maintains its organization by regulating the flow across its blanket.

Why You Can Never Touch Reality

Here's the unsettling implication: you can never perceive reality directly.

Everything you know about the world comes through your sensory blanket. Photons hit your retina. Sound waves vibrate your eardrum. Chemicals bind to receptors in your nose. These are the signals—the only signals—you ever receive.

But the signals are not the world. They're patterns at the blanket surface that your brain must interpret, infer, guess about. What's out there? You don't know. You can't know. You can only hypothesize, based on the shadows that cross your membrane.

This is Plato's cave, reframed in probability theory. You're chained inside a statistical boundary, watching shadows cast by a reality you can never directly witness. All perception is inference. All knowledge is hypothesis. All experience is the brain's best guess about what lies beyond the blanket.

This sounds nihilistic, but it's actually the opposite. The fact that you can function—that your guesses are good enough to navigate, survive, thrive—is remarkable. Your blanket is well-tuned. Your inference engine is sophisticated. You're very good at building models of what you can't see.

But you should stay humble. The model is not the territory. The inference is not the truth. There's always more beyond the blanket than you can know.

The Blanket as Immune System

The Markov blanket doesn't just passively transmit signals. It actively regulates them.

Think of your immune system. Its job is to distinguish self from not-self—to identify foreign invaders and neutralize them while leaving your own cells alone. This is blanket regulation at the molecular level. The immune system patrols the boundary, deciding what crosses and what doesn't.

Your psychological boundaries work similarly. You don't absorb every piece of information that arrives at your senses. You filter, select, weight, ignore. Some signals get high priority; others get screened out. This is precision weighting at the blanket—the regulation of what counts as informative.

Healthy boundaries mean a well-regulated blanket. You let in what you need. You keep out what you don't. You're permeable enough to learn and connect, impermeable enough to maintain coherence.

Unhealthy boundaries mean dysregulated blanket function. Too rigid, and you can't let new information in—the model becomes stale, disconnected from reality. Too porous, and you're flooded—every signal overwhelms, no filtering possible, the inside colonized by the outside.

Trauma often damages the blanket. The overwhelming event was precisely one where the normal regulatory function failed—where more crossed the boundary than the system could integrate. The aftermath may involve desperate attempts to thicken the blanket (withdrawal, numbing, avoidance) or persistent porosity (hypervigilance, reactivity, flooding).

Blankets Within Blankets

Here's where it scales.

You have a Markov blanket. But so does your brain. And within your brain, so does each neural population. And each neuron. And each synapse. It's blankets all the way down.

At each level, the same logic applies: internal states maintain their organization by regulating flow across the blanket. A neuron minimizes prediction error across its membrane. A brain region minimizes prediction error across its interfaces with other regions. The whole brain minimizes prediction error across the sensorimotor boundary.

And it scales upward too.

A couple is a system with a blanket. The blanket is their communication interface—the signals they exchange. Inside the blanket: the shared understanding, the relational dynamics, the "us" that emerges from their coupling. Outside: the rest of the world they engage as a unit.

A family has a blanket. An organization has a blanket. A culture has a blanket. At each level, internal coherence is maintained by regulating what crosses the boundary.

The same mathematical structure repeats at every scale. This is why the same principles—prediction, surprise minimization, coherence maintenance—apply from neurons to civilizations. The architecture is self-similar. The blanket is fractal.

The Self as Process

If the self is defined by its blanket, then the self is not a thing. It's a process.

A thing is static—a fixed entity with persistent properties. But the blanket is dynamic. It's constantly changing what it lets in and lets out. The internal states are constantly updating. The boundary itself can shift, expand, contract.

You are not the same self you were a decade ago, or a year ago, or even this morning. The internal states have transformed. The blanket has been renegotiated. What counts as "you" has shifted.

And yet there's continuity. The pattern persists even as the contents change. The organization is maintained even as the components turn over. This is what it means to be alive: to maintain a coherent pattern against the flow of time and entropy.

The self is the invariant in the flux. Not a substance, but a structure. Not a thing, but a pattern of prediction and action that keeps itself organized across its blanket.

Dissolving Boundaries

Some experiences involve the sense that the blanket has dissolved.

Mystical experiences often include feelings of unity, boundarylessness, merger with the world. The usual separation between self and environment seems to evaporate. Subject and object collapse.

Psychedelics reliably produce this. So do certain meditation practices, certain kinds of awe, certain moments of deep connection or presence.

From the blanket perspective, these might involve temporary relaxation of the boundary regulation—a loosening of the precision weights that normally distinguish inside from outside. The models stop sharply separating self from world. Prediction error about where "I" end becomes tolerable. The blanket becomes permeable in ways it usually isn't.

This can be profound or terrifying, depending on whether the loosening is chosen and supported or forced and overwhelming. Controlled dissolution can produce insight, expansion, transformation. Uncontrolled dissolution is psychosis—a blanket so porous that no stable self can maintain itself.

The boundary is protective. But it's also a limit. Sometimes growth requires renegotiating it—letting in what was screened out, extending into territory that was foreign. The art is doing this without losing coherence entirely.

Digital Blankets

Technology extends the blanket.

Your smartphone is part of your interface with the world. Information flows through it to you. Your actions flow through it to affect the world. It's become part of your sensorimotor membrane.

Social media extends the blanket in complex ways. Suddenly you're receiving signals from thousands of people you've never met. Their states influence yours. Their judgments cross into your interior. The bandwidth of the blanket has exploded—more information flowing in than any human blanket was evolved to handle.

This creates new boundary challenges. How do you regulate a blanket that extends into global information networks? How do you maintain coherence when you're permeable to the emotional states of millions?

Many contemporary pathologies might reflect blanket dysregulation in the digital age. The anxiety of constant connectivity. The depression of comparison culture. The fragmentation of attention across too many signals. The loss of clear boundaries between self and feed.

The Markov blanket was tuned by evolution for small-group, face-to-face, relatively stable environments. We've blown the boundaries open. Learning to re-regulate them is one of the central challenges of our time.

Protecting the Membrane

Mental health might be, at its core, blanket health.

The capacity to regulate what crosses—what signals you let in, how heavily you weight them, what actions you emit, how you maintain internal organization despite external pressure.

Therapy often involves blanket work, whether or not it's framed that way. Learning to establish boundaries. Learning to tolerate signals that used to overwhelm. Learning to filter more effectively. Learning to act in ways that create the environment you need rather than being passively shaped by the environment you have.

Relationships are blanket negotiations. Two people with their own blankets must work out how to interface. What do you share? What do you protect? Where does your internal space end and theirs begin? Healthy relationships maintain both individual blankets and a shared blanket—each person's coherence preserved while a new "we" emerges at the junction.

Culture provides blanket scaffolding. Norms, expectations, roles—all of these help regulate what crosses between people, making social life predictable enough that individual blankets don't constantly flood. When culture fragments, this scaffolding fails. Everyone's blankets are less protected. Coherence becomes harder to maintain.

The Membrane of Meaning

Meaning happens at the blanket.

It's not inside you, exactly—your internal states alone don't constitute meaning. It's not outside you, exactly—the world without your engagement is just physics. Meaning arises in the transaction across the boundary. In the prediction that meets the outcome. In the action that shapes the environment. In the continuous back-and-forth between model and reality.

Meaning is coherence across the blanket. When your predictions align with what arrives. When your actions produce what you expected. When inside and outside speak the same language, follow the same patterns, move in coordination.

Meaninglessness is blanket failure. When predictions miss. When actions don't produce expected outcomes. When inside and outside no longer correspond. The world beyond the blanket becomes alien, opaque, unnavigable.

You are your blanket, in a sense. You are the boundary that separates your particular pattern of organization from the undifferentiated chaos outside. You are the process that maintains that separation—not perfectly, not permanently, but well enough and long enough to be called a self.

The membrane between you and everything else is invisible. But it's the most important thing about you.

It's what makes you you.