The boundary of the epistemically possible
(a post I drafted a long time ago but never got the time to clean up & publish until now)
It may not be obvious or intuitive, but somewhere between “we don’t know yet” and “we can’t ever know” there’s a line, and almost every argument about the divine/God, consciousness, or the limits of science is secretly an argument about where that line sits. Nobody agrees on where it is. Nobody can even agree on how you’d go about finding it. And the more you sit with the problem, the weirder it gets, because to draw that line you’d need to stand on both sides of it at once.
The unknown and the unthinkable
“We don’t know” hides two fundamentally different conditions. The first is ordinary ignorance (which I call a “gap”): the answer is something a human mind could in principle understand, we simply haven’t reached it. We may lack evidence, instruments, computation, or the right theory. This kind of unknown lies somewhere inside the human epistemic search space, even if it is currently far beyond us.
The second begins where that search space itself ends (which I call a “wall”). Human cognition is not disembodied reason looking directly at reality. It is something performed by a particular biological nervous system, with particular senses/ intuitions/ representational capacities, and forms of thought. That neuralbiological architecture determines the limits. E.g. an ant doesn’t understand three-dimensional space very well / can't do calculus. We cannot explore in a cognitive direction our brains have no way to represent.
There is no reason to expect reality to fit perfectly within the conceptual range of one evolved primate. Some truths may therefore be not merely undiscovered but humanly unthinkable. We might be unable to formulate the relevant question, or we might be given a perfectly accurate answer and still lack the mental structure required to understand it.
Our tools can push these limits outward. Instruments translate signals our senses cannot detect, mathematics carries us beyond intuition, etc. But a system might tell us exactly what reality will do while the structure behind its answer remains cognitively inaccessible to us.
So one kind of not knowing concerns territory we have not yet reached, the other concerns territory that cannot exist within a human cognitive map at all. The first is a frontier, the second is a wall imposed by the neurobiology of the mind doing the knowing.
God is the name we give the wall
“God” has historically functioned less like a claim about the universe and more like a placeholder, a variable name assigned to whatever sits on the far side of our structural limits. When the ancient world couldn’t explain lightning, nobody said “we lack data”; they said “Zeus.” Not because they were stupid, but because that’s what you do when you hit something you can’t get past and don’t yet know if it’s a wall or just fog. You try to name it, and the name lets you stop staring at the hole in your model and get on with your life, because naming the phenomenon is enough to work with it. “Magic” is just the variable name for phenomenon x that exceeds my current causal model.
Reinvented Kant
We’re not the first people to notice this wall, and the shape we just drew it in is almost exactly the shape Immanuel Kant drew 250 years ago, minus the vocabulary.
Kant’s move in the Critique of Pure Reason was to argue that space, time, and causality aren’t features of reality we discover; they’re categories our minds impose on raw experience before we ever get to “look” at anything. We never encounter the world directly. We encounter the world as filtered through the only cognitive apparatus we have. He called the world-as-it-is-in-itself the noumenon, and the world-as-it-appears-to-a-mind-shaped-like-ours the phenomenon, and his entire, unnerving claim was that the noumenon is not merely hard to access. It’s categorically inaccessible, forever, to any mind built the way ours is (neurobiologically). A wall by construction.
It’s one of the oldest ideas in modern philosophy, and the fact that it keeps getting independently reinvented (by ant-and-algebra thought experiments, by a philosopher wondering what it’s like to be a bat, by cognitive-closure arguments, etc.) should probably update you toward taking it seriously. Ideas that keep getting rediscovered from different starting points usually aren’t accidents.
Admitting the wall isn’t defeat
Saying “there is a hard limit and we’ve reached it” sounds like giving up, but it might be the more honest position, and the more useful one. Assume everything is eventually knowable, and you’ll spend forever trying to teach an ant integral calculus, and mistake stubbornness for rigor. Admitting some questions might not be shaped for your mind at all and redirecting the energy toward the ones that are might be more pragmatic.
You can’t draw the line without seeing over it! or can you?
Then it gets genuinely (maybe unsolvably) hard: to know something is a permanent wall and not just a very stubborn gap, you’d need to somehow verify there’s nothing on the other side. Verifying that requires looking, and looking past a wall you can’t see past is, definitionally, impossible.
The ant has no way to check whether algebra is just very advanced pheromone math or something entirely outside its universe. It can’t run the experiment; it doesn’t even know there’s an experiment to run.
But we’re not ants, and sometimes we can notice the wall without being able to see past it. We can ask why there is something rather than nothing and feel the question mean something, even while suspecting we’re structurally incapable of holding the answer. An ant doesn’t know it doesn’t understand 3D space; it just lives. We spend our whole lives with our faces pressed against the glass, and the fact that we can find the glass at all might mean we’re already standing right at the edge of what we’re built to hold.
The one wall we’ve actually proven exists: Gödel’s incompleteness theorem
Almost every wall discussed so far is suspected, not demonstrated. We think God, consciousness, or the noumenon is out of reach. Nobody has proven it in the way we prove a theorem. Which makes one case worth pulling out specifically, because it’s the single instance in the entire history of thought where a wall wasn’t guessed at but was derived.
In 1931 Kurt Gödel proved that any formal system powerful enough to describe basic arithmetic will contain true statements the system cannot prove from within itself. Not “hasn’t proven yet.” Cannot, ever, using only its own rules. The system can even construct the sentence, a version of “this statement cannot be proven within this system,” and represent exactly what it says, without being able to close the loop on it from the inside.
Notice what that is. It’s the recursive trap from before, given a rigorous, mathematical spine: a system that can formulate the boundary without being able to cross it. You can see the wall precisely because you’re standing close enough to touch it, and touching it is exactly the thing you can’t do. Gödel is the only place where “here is a wall, and here is the proof that it’s a wall, not a gap” both exist in the same sentence. Every other wall in this essay is a hypothesis about a Gödel sentence we haven’t been able to write down formally. That doesn’t mean the hypothesis is wrong. It means we’re arguing from analogy in every case but one, and it’s worth remembering which one that is.
To guess where the wall is
Since we can’t step outside our own skulls to check, we’re stuck with heuristics. Imperfect, but not useless.
For example, Noam Chomsky splits the unknown into problems and mysteries. Problems have parameters. You might not have the answer yet, but you know roughly what an answer would look like; how gravity relates to quantum mechanics, say. Progress is slow, but it’s progress. Mysteries are different. You stare at them for centuries and never converge; you don’t even agree on how to ask the question properly. Different eras just produce different flavors of confusion.
Intelligence vs. consciousness
Intelligence looks like a problem, not a mystery. We can decompose it. Crack open a transformer, trace the circuits, find the induction heads, follow the weights. The fact that we can build the thing, even without fully understanding it, tells you it lives inside our domain.
Consciousness looks like a mystery, but the mystery itself has a live counterargument, and it deserves airtime. The counter-tradition, usually called illusionism, is associated most with Daniel Dennett until his death in 2024, and carried forward now by Keith Frankish. The argument: the thing that actually needs explaining isn’t why physical processes produce felt experience, but why physical processes produce systems that insist they have felt experience that can’t be explained physically. Interestingly, the term for this reframe (the “meta-problem of consciousness”) was coined by Chalmers himself, not by the illusionists, as a genuine philosophical tool he thought was worth taking seriously regardless of which side you landed on. The meta-problem asks: why does introspection generate the intuition of an unbridgeable gap, whether or not the gap is actually there? That’s an empirical, tractable question. If it turns out fully explicable (a known kind of representational output, the way a visual illusion is explicable), the hard problem doesn’t get solved so much as it evaporates, the way “why does the sun move across the sky” evaporated once we understood we were actually the ones moving.
It’s a major challenge to mysterianism, and also a core challenge to our question’s framing (gap vs. wall as two different types of unknown). How do you even know if something is a wall, or just a very convincing illusion generated by a gap?
But maybe not so permanent after all
“Permanent boundary” assumes a fixed subject: this boundary, for this mind, forever. But minds aren’t fixed. An ant with no external tools will never do algebra. An ant wired into some hypothetical prosthetic that did the algebra for it, translating the output back into pheromone trails it could act on, arguably would. Not because its brain changed, but because its effective cognitive boundary moved.
And with future advances in BCI, etc., maybe our neurobiological architecture itself (which dictates the limit of what’s epistemically possible for us) can be hacked or changed. So even if some walls are real, they’re not necessarily permanent.
The only method that actually works
Back to the original question: how do you tell if it’s a gap or wall?
You don’t. Not in advance, and maybe not ever, except in the one case with a proof attached. The only method anyone’s found for the rest is to keep walking toward it until you either break through or you don’t. Calling something a “permanent boundary” today risks the exact mistake people made in ancient times calling lightning “Zeus.”
The honest stance was never about deciding, right now, which side of the line a question falls on. It’s about pushing as hard as you can, for as long as you can, while staying honest about the moment your tools start to bend and squeal under the weight of the question.
I’d like to think the only way to know a wall is real is by the bruises you get running into it. And we should keep running into it.