What Stands Between You and Reality?
- Spencer Greenberg and Travis M.
- 49 minutes ago
- 12 min read
Short of time? Read the key takeaways.
🔗 Your perception of the world around you is shaped by many hidden steps. Even before you form a simple thought like “There’s a cat on the table,” your senses and brain have already selected, processed, organized, and interpreted information—creating several opportunities for details to be lost or errors to creep in.
👁️ Your senses capture only a thin sample of reality. Humans detect some features of the world but miss many others. Non-human animals detect things we don't, and fundamental physics may impose additional limits on what can ever be observed or known.
🧠 Perception involves your brain constructing a model of the world from sensory information. Many philosophers describe conscious experience as involving a brain-generated representation—what this article loosely calls a “simulation”—rather than a passive recording of reality. Illusions show that this representation can sometimes mislead.
🗂️ We make the simulation manageable by carving it up with concepts that might not reflect reality. We compress the data by carving it up and categorizing it. We call this region of reality a "suit", and that region a "tea set" (for example). But the reason we believe in suits and tea sets (rather than carving reality up some other way) is because those concepts serve our purposes, helping us navigate the world. Since purposes are only in our heads, at least some of the ways we carve up the world plausibly doesn't reflect mind-independent reality.
🔦 We pay attention to only a tiny fraction of what we could notice. Our goals, expectations, interests, and training determine which parts of a scene reach awareness, while most of the available information is ignored.
📖 We turn what we notice into meaningful stories. Our memories, identities, motivations, worldviews, and social groups shape what events mean to us—which helps explain how people can interpret the same evidence in radically different ways.
🧘 Recognizing these layers should inspire epistemic humility. Since our experience is built up through multiple layers, each of which is susceptible to error, it is appropriate to:
Treat our beliefs as slightly more uncertain than we otherwise would
Adjust our confidence to fit the reliability of the processes that produce our beliefs
Stay open to other people's perspectives
When we look at the world, it feels like we perceive facts directly. You see a cat on the table and think, "There's a cat on the table" – a direct translation from perception to knowledge. But even the simplest of beliefs about what we perceive involves many interpretations and judgments that people rarely notice they’re making. Each of those interpretations and judgments is a place where error can occur. Either information gets left out, or bias creeps in. That means that even when it feels like we're perceiving the facts directly, by the time we finally arrive at a belief, a great deal of error can have accumulated. For a cat on the table, this is rarely consequential, but for other domains the accumulation of uncertainty can be more profound.
As we'll explore in this article, there are a surprising number of layers between the world and our perceptions of it. Beliefs about what we perceive are the result of a long chain of noisy translations between those layers. By reflecting on this, we can deepen our appreciation of an important aspect of critical thinking: epistemic humility, born out of understanding our limitations.
So, let’s walk up this chain, examining five layers. We’ll start with data taken in by our senses, and end at the stories we tell.
Layer 1: Our senses take in only some of the data
A thermometer detects temperature, but not pressure. A barometer detects air pressure but not light. Our sense organs can detect a variety of aspects of our environments, but there’s plenty they leave out. Nature is replete with fascinating examples of life with alien-seeming ways of taking in data about their surroundings, including:
Some snakes have an organ in their faces called a “pit” that can detect infrared radiation, allowing them to see “thermal images” of the world.
Many birds are able to sense information about the Earth’s magnetic field. They appear to detect the direction of the field (which they can use as a compass) and magnetic intensity (which they use to build a “map”). Researchers are still not totally sure how this is achieved.
Most fish have what’s called a “lateral line” system that senses the flow and pressure of water, allowing them to rapidly adjust their body position in response to changes in water flow (“rheotaxis”), seek prey, evade predators, and more.
Not to mention echolocation in bats, chemotaxis in bacteria, the fact that bees see ultraviolet light (which means that flowers look very different to them than to us), and many more.
This points to the fact that some of the limitations of our senses are accidents of evolution. If we rewound history and let evolution play out again, especially if the environment was different, perhaps we’d see a human-like species evolve with very different sensory modalities. Perhaps we’d take in very different data from our environments.
But not all limitations on what we can observe are the result of evolution. Some could be limitations imposed by fundamental physics. For example, the uncertainty principle in quantum mechanics tells us that there are pairs of properties (e.g., position and momentum) such that there is a fundamental limit on how precisely they can be determined together: increasing the precision of one necessarily limits the precision of the other. There are several ways to interpret this, including but not limited to:
There exist features of reality that are (in principle) undiscoverable by us, such as definite, precise values of the position and momentum of elements in a quantum system.
Quantum systems simply do not have definite, precise values of position and momentum at the same time.
Physicists and philosophers haven’t settled on an interpretation. But if the first interpretation is the right one, then there’s information we simply cannot know. This would be another way in which our ability to take in data about the world is limited.
All of this means that before human psychology even enters the picture, there’s already a chasm between us and the “true”, mind-independent nature of things out in the world.
Rather than reading reality as it really is in itself, we take only a thin sample of its features.
Layer 2: Sensory data turn into simulations
To simplify matters somewhat: when light hits your eye, a chemical reaction occurs, which kicks off electrical signals that get sent to your brain. The electrical signals carry information about the light (not light itself), which is processed by your retinal tissue and brain, and out of that, a visual experience is produced.
This kind of explanation has led many philosophers to conclude that what we apprehend in experience is not actually a passive or unprocessed picture of the world outside ourselves, but something that involves a representation or model of that world, created by our brains, built out of the data from our senses. In this article, we refer to this loosely as ‘simulation’.
The Enlightenment philosopher John Locke most famously divided the qualities (a.k.a., traits, features, properties) of objects into two types, which he called “primary” and “secondary”. Primary qualities are the ones like size and shape, which (he argued) exist in objects whether or not they are being perceived, and our mental simulations resemble these qualities in the objects themselves. But secondary qualities do not resemble our mental simulations of them.
Take color, for instance: color is your brain’s representation of certain wavelengths of electromagnetic radiation that bounce off objects (along with some other, more technical details). If the world contained no beings with sense organs capable of detecting electromagnetic radiation, or no brains to turn those sensory data into simulations, there might well be light waves bouncing around, but there would be nothing that has the character of experiences of redness. Out there in the world, light of certain frequency bands is hitting our eyes. Inside our minds, the experience of red is happening.
Other secondary qualities include smell, taste, and sound. Hence the famous question of whether a tree that falls with nobody to hear it makes a sound. Given what we’ve discussed in this section, many take the answer to be that pressure waves would propagate through the air, but there would be no sound (at least, that's the case if sound is defined as involving an experience occurring).
But, regardless of what kind of quality you’re observing in an object, your observation is not a passive recording of reality; it involves your brain’s representation of the measurements made by your sense organs.
Two distinct sorts of failures can occur at this layer.
First, there can be failures in how your senses collect that data, as might happen if your optic nerve is damaged or if cataracts tint the light entering your eyes.
Second, there can be failures in the creation of a simulation by your brain, where it fails to faithfully represent some aspect of the external world. We see this most easily with optical illusions. One reason we find such illusions so interesting is that they lay bare the fact that our brains’ renderings of reality can come apart from reality itself.
We can only tell these are illusions because we can check our internal rendering against something more objective and discover a mismatch (e.g., by using a ruler or checking the color value of different pixels). But the unsettling implication is that the renderings we can’t easily check are sometimes misleading, too. We may lack the awareness or the right ruler to catch them.
Layer 3: We bucket the simulation
A raw field of colors and sounds may approximately reflect how an infant experiences the world, as its brain learns furiously how to structure things. But that unstructured representation isn’t yet a representation you can use to plan actions in. To use your experience effectively, your mind has to carve that experience up. It has to decide that this represents a table, that is a person, and that other part is the floor.
This chunking (technically called “individuation”) and categorization happens automatically and below conscious awareness. It’s enormously useful, but it’s another layer of interpretation laid on top of an already-imperfect simulation, and it can distort things in its own ways.
For one thing, have you ever stopped to wonder why we tend to think there can be a single thing called a “suit”, composed of two disconnected items of clothing (a jacket and trousers), but there’s no single thing made up of your left shoe and your right glove? Or why do we tend to think there can be a single thing called a “tea set” (composed of a teapot, milk jug, sugar bowl, cups, and saucers) but no single thing composed of a teapot, a vase, and a cereal bowl (even if they are aesthetically matching)?
Philosophers investigating this have argued that the common-sense way we automatically chunk the world into objects is driven by purposes. Treating suits and tea sets as unified objects serves our purposes, but treating shoe-gloves and random collections of crockery as unified objects doesn’t. Hence, we think there are such things as suits and tea sets and no such things as shoe-gloves. The troubling thing is, those philosophers argue, that purposes only exist in our heads. They’re not objective, mind-independent features of nature. So the common-sense way we carve the world up into discrete objects doesn't seem to reflect mind-independent reality as much as we might think.
For another thing, even when we have established ways of chunking up the world, we can apply them in mistaken ways. We can mistake a coat on a chair for a person the moment we enter a room. Or, if you’re Spencer, you can briefly think you see cats in the dark when on vacation because you see cats in the dark when you’re at home.
On top of all that, our categories often take genuinely complex things and force them into simplified buckets. If you're not a bird person, then you may when walking in a park, stumble on a rare bird (the last of its species, on the brink of extinction), and your brain will just label it “bird”.
Tremendous variation can hide inside even simple-seeming categories, let alone complex categories like “tree”, consisting of tens of thousands of species.
So, the way we carve up our simulations and put things into individual buckets is biased by our parochial human purposes and produces compression, ignoring nuances in the data. This makes the world manageable, but sometimes a lot is lost in the process.
Importantly, the more you pay attention to a type of thing and the more you understand about it, the more refined and subtle your buckets are likely to become. You’ll go from thinking “That's a tree.” to “That’s a Sycamore tree.” to “That’s a Platanus wrightii – also known as an Arizona Sycamore.”
Layer 4: We ignore almost everything
Even with the compression achieved by this chunking up of reality, there’s far too much information for us to process, so our brain uses another heuristic: if something doesn’t draw our attention, it’s ignored.
A famous experiment studying “inattentional blindness” found that when people were told to carefully count how many times a basketball was passed, they failed to spot a person in a gorilla suit walking between the basketball players (you can view the video here).
If you’re having a conversation with Spencer (one of the authors of this piece) you can play a trick on him: ask him to close his eyes, then you ask him to recall what you were wearing; he’ll be clueless, despite having been looking at you moments ago. Heck, with his eyes closed, he may not even be able to tell you what he’s wearing.
On the other hand, if you try the same thing with a person who is an expert in fashion, they’ll likely not only be able to describe what you are wearing, but also make an informed guess about the brand.
We notice what we find interesting, important, or surprising, as well as what we’ve trained ourselves or been trained to notice. And we are unaware of most of the rest. This (in part) explains why eyewitness testimony has proven to be much more fallible than a lot of people assume.
You didn’t know that person was about to rob the store you’re in, so even though they walked right in front of you, chances are you have no recollection of what they look like. Even when you realized that they were robbing the store, your attention likely was drawn to the knife in their hand or the exit door, rather than the contours of their brow, lips, and nose.
Our limited attention acts as yet another filter on what makes it into our experience. But one layer remains.
Layer 5: We turn noticed chunks into meaningful ones
Even once you’ve chunked the world into objects and categories, and you’re actually paying attention to some of them, the process of perceiving isn’t complete. Your brain still has to decide what it all means.
A Sycamore tree has no special significance to Bob, whereas to Sally it’s where she had her first kiss, and to Elio, it’s what his grandfather died under. To Spencer, it was a phrase served in an ad when he was looking for a type of tree to use in this example.
Once we’ve chunked a scene, it gets woven into a story. Our reflective minds run on such stories. The stories tell us what’s important, what’s threatening, and what’s good. But this final layer of interpretation is steered heavily by things that have nothing to do with the scene itself: our identities, our motivations, our worldviews, our past experiences, our anticipations, and our social groups.
This is why two people can look at an identical event – even identical data represented in a chart – and walk away with opposite understandings. They are running the same data through different meaning-making machinery constructed within different lives.
Of course, that’s not how this all feels. The meaning we make feels like it’s obviously the way things are. The one true story. Or, not even a story – just reality itself.
What this teaches us about critical thinking
The layers discussed in this article are a metaphor and (like any helpful metaphor) involve some simplification. Ultimately, reality is messier than this model because perception doesn't always happen in this neat order. For example, what you pay attention to (layer 4) can affect what data you take in (layer 2). That said, the layer metaphor captures some important facts about our relationships with reality and it has useful things to teach us.
We seldom pay attention to the ways our senses have left out information (or cannot access it). We ignore the electrical signals that flow through our retinas and the bucketing we did to compress the information. And we rarely consider alternative stories our brains could have told us (but didn’t) about what we did pay attention to.
This means we often ignore the ways the world seems to others. Whether that’s non-human animals with different sensory modalities, or people whose brains chunk up the world in different ways, or who ignore or focus on different things than we do, or who tell different stories about the same observations.
This may sound disheartening, but it’s not a complete epistemic disaster. Despite all this, we know a lot about how to get reality to do things for us. Science often works to discover new truths. Bridges rarely fall. Some stories are accurate, even if they aren’t complete.
We think that the ultimate lesson to be learned from all of this is epistemic humility.
It helps to remember, from time to time, that what we’re experiencing is a model or a simulation, which is a series of translations removed from whatever is actually out there in mind-independent reality. And, as a result, it helps to aim to think of our estimates and opinions as at least somewhat more uncertain than we otherwise would, and to make sure our degrees of confidence take into account the reliability of the processes that generated our beliefs.
Doing so has the happy effect of making it easier to consider alternative perspectives that contradict our own. That’s useful societally, where there’s an overabundance of perspectives that are rigidly held. But it’s also helpful in relationships, friendships, and our work.
We’ve argued that nobody has access to the reality beyond their processed and interpreted simulation of it (that reality is not actually the sort of thing that’s capable of being seen), but we can all, at least, stop mistaking the top of the stack for the bottom.
If you enjoyed this article, you might enjoy our free Faulty Reasoning Quiz! Learn about five types of faulty arguments and see how well you can spot them:
