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Christian95's avatar

How do we know that all we see is real?

Asked by Christian95 (3253 points ) October 27th, 2009

I know the question is a little bit confusing but try to understand.I’m asking how do we know that our brain isn’t inventing all this.How do we know that all this isn’t just an illusion?

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56 Answers

whatthefluther's avatar

There is no such thing as fluther.com You dreamt the whole thing. Now wake up. See ya….Gary/wtf

ragingloli's avatar

we do not.

Cartman's avatar

How very Matrix of you.

Everything we see and experience is an interpretation of our sensory systems. Sensory function differs from person to person (some are way outside what is considered normal).

Thus, the brain IS inventing everything you experience and therefore there is no real telling if it is true…

More sedate

Janka's avatar

Short answer: we don’t.

Longer answer: where you take it from there is your call. Personally, I find that the assumption that what I see and experience corresponds to some physical reality (though far from exactly) still helps me function within the world I perceive.

My perception is that things have causes and consequences—if I put my hand in the fire, I hurt. Whether that hurt is “just an illusion” or not is largely irrelevant to my experience.

My perception is that there are other thinking beings like me. While it is possible that this is just an illusion and in the end it does not matter whether I cause “pain and suffering” to them, because “really” they do not exist, I would rather not take that risk. So I work from the assumption that other beings’ hurts also matter.

As a wise man once said to me, all models (worldviews, theories, explanations of the world) are false—but some of them are useful.

knitfroggy's avatar

This question makes my head hurt this early in the morning.

Why wouldn’t what we see be real? Besides if this were some type of false reality I’d hope to hell I’d be rich and better looking.

cookieman's avatar

Well it’s “real” because it’s a shared experience. If you see a brown dog napping under a tree and the guy next to you sees a brown dog napping under a tree – it’s real.

As @Cartman mentions, we all may experience the same thing differently. Our senses may interpret it differently. So someone else may see a red wolf laying near a bush. Still real – different interpretation (slightly exagerated for effect).

Now is it possible that what everyone experiences isn’t real (a la Matrix)? Sure, I suppose so. But you would drive yourself nuts thinking about it. And if (mostly) everyone experiences the same occurances – that’s “real” enough for me.

Harp's avatar

@cprevite Just for the sake of discussion In my dreams, there’s a shared experience too. If I were to interrogate the population of those dreams, I think they’d corroborate my experience.

Discussions like all this tend to end up at the question of what we mean by “real”. Unless that gets pinned down, the discussion can’t really go anywhere.

dpworkin's avatar

Actually, you are hallucinating all the time, because that is how our brains have adapted to vision. The sensory impulses generated by photons impinging on the retina cause signals to be sent to the occipital lobe where information as to location, shape, size, etc are detected, and then sent eventually to the frontal lobe where they are interpreted, but your brain is constantly “filling in” missing information by making assumptions. That explains, as just one example, why you think objects are moving when you are watching a film, when of course you are actually just seeing a series of still photographs.

As to the philosophical dimension of your question, it goes back thousands of years and has been resolved in the West, at least, largely by the empiricists. You can read what hundreds of brilliant philosophers have decided about this and other questions through a process called reading, a form of which you are doing here.

pinkparaluies's avatar

Another Matrix comment right here. knock knock knock

Grisaille's avatar

You don’t. We don’t.

Throw me in the “external reality is an internally created state” camp. For example, there is no way to know if your “blue” sky looks “red” to another person – that is to say, everyone sees the world in different colors, or at least calls the colors different names than you would. It’s early, and I don’t feel like explaining what I mean, so just figure it out.

Put bluntly, even if this reality was an illusion, it was (or we were) built to inhabit it relatively safely. Philosophically, there is no way to disprove or prove anything to be an absolute truth or falsehood, so asking this question is akin to asking, “what if this universe is some 5th grader’s failed science project, and we’re living in a shoebox under his bed collecting dust?”

There is no evidence for either question, but there is no evidence to prove it completely false, as it starts to creep on the boundaries of scientific understanding. So stop worrying.

LostInParadise's avatar

The doctrine you are talking about is called solipsism. One way to attack it is to apply Occam’s Razor. There is no practical benefit in assuming everything is in your mind. In fact you would have to come up with some complicated scheme to explain the consistencies – if you place an imaginary object in an imaginary box, then why is it that you see the object every time you look in the box? It makes things simpler if you make the simpler assumption that things have an independent existence.

Another approach would be to confront the problems at the boundary of you and the rest of the world. Is your body real? How do you explain the act of raising your hand? If you hit your hand with a hammer, how do you explain the pain that you feel if the hammer is only imaginary?

Grisaille's avatar

Also, “I know the question is a little bit confusing but try to understand” is rude. Just because you don’t understand what you’re asking does not mean that we don’t. I know you’re 14 (I’ve seen you post similarly arrogant questions and answers), but lighten up. The populace is a much more intelligent creature than you think it is; you’d do well to stop being a pompous jerk.

ragingloli's avatar

“If you hit your hand with a hammer, how do you explain the pain that you feel if the hammer is only imaginary?”
The brain itself simulates the pain it expects from analysing the visual data it itself created.

RareDenver's avatar

@ragingloli so what if someone hit your hand with a hammer while you were looking the other way, I don’t know maybe a bit of furry porn caught your eye and you were distracted?

LostInParadise's avatar

And why would your real brain create real pain in response to an imaginary hammer?

dpworkin's avatar

Folks, these are what is known as “Sophomoric” questions. They are more fun when everyone is stoned.

ragingloli's avatar

@RareDenver
“so what if someone hit your hand with a hammer while you were looking the other way, I don’t know maybe a bit of furry porn caught your eye and you were distracted?”
The analysing of the visual data was actually superfluous.
You would still feel the pain because the hammer blow is planned to happen in the simulation even though your consciousness would not be fed the data of that prior to the pain.

Cartman's avatar

If you’re blind you don’t see anything.

dpworkin's avatar

Nonesense. My girlfriend is blind and she sees plenty.

Cartman's avatar

@pdworkin silly me, I thought the definitions of blindness was a person lacking the sense of sight?

ragingloli's avatar

some researcher once hooked radar to his brain and after a while his brain adapted to the new input and he could sense his surroundings. possible solution to blindness.

Bluefreedom's avatar

Unless you have a sit down with Morpheus and he convinces you that you’re nothing more than a battery helping to power the construct, what you see is real. Additionally, if someone asks you if you want to take a pill, I’d lean toward swallowing the blue one. Or is it the red one? Choose wisely.

RareDenver's avatar

@Bluefreedom I’d neck them both and see what happens :-)

Harp's avatar

Everyone who’s at all reflective stumbles upon this question at some point, and I imagine that to all of them it seems strange and wondrous because, frankly, it is. If @Christian95 is discovering it now and trying to get his head around it, I congratulate him on this right of passage as an independent thinker.

If this matter has already been expounded upon by generations of brilliant minds, it’s because it is an extremely compelling question, and because it’s far from being a settled question. When it arises for each individual, it may be helpful to take a look at what others have done with it, but I don’t believe that it’s a simple matter of choosing sides in an ancient debate and then forgetting about it.

Ultimately, this question is about the nature of experience itself, and so experience is the laboratory where the investigation must take place. Looking at the experience of others is unnecessary; your own is right there at all times. Question it and whatever assumptions you already have acquired about it. That’s one of the richest adventures life has to offer. It’s not just for stoners.

fireside's avatar

Looking at it another way is fun too.

How do we know that the limitations we perceive are real?
How different would our goals be if we didn’t perceive the limitations?

ShanEnri's avatar

If our brain is inventing all that we see, wouldn’t that make it real to us?!

drdoombot's avatar

The more important question is: does it matter if the world is real or an illusion?

If you drop an anvil on your foot and you feel pain, does it make a difference if the world is real or not? In either case, there is a set or rules or a logic for all actions, real or not. In a real or imagined world, when you get hungry, you must eat. If you cut yourself, you must stop the bleeding (or die). If a car hits a loved one, they might leave your life forever.

The point is, the responses and reactions available to to you in a real or illusory world are the same. The most important thing to consider is how you should act (or react), and there are thousands of philosophy books that discuss that subject as well.

jackm's avatar

Because there seem to be rules that exists outside of my head I can not break. When I am dreaming, I can break those rules.

dpworkin's avatar

@Harp I think you are correct, which is why I answered the OP’s question. But not all of the ancillary questions seemed to me to have as much merit.

Jeruba's avatar

The answer depends on how you define “real.” And “know.”

And, for that matter, “see” and “we.”

And “is.”

wundayatta's avatar

One way is if other people say they see the same thing we see. Another is if we can interact with the external world in a predictable way—i.e., reality works the same way all the time. Another is that our senses give us consistent information. Most of us, anyway.

Another is realizing that the issue of reality is moot. We can’t make everything do what we want it to do, simply by willing it. We have no choice but to act as if our perceptions are an accurate reflection of what’s out there. We can have different theories about how to explain what is out there, and we can choose to believe a theory that says the world is only in our heads, but that doesn’t change what is possible.

HGl3ee's avatar

We will never truly know until we can better understand the HUGE portion of our brain that we don’t use ;) – LB

Grisaille's avatar

@ElleBee The whole “we only use 10 percent of our brain power” is not factual – an old wives tale, if you will.

There is, has been and probably never will be any evidence that supports the claim that we use a “fraction” of our brain. Even if some ariesel, it’d be thrown away for a simple reason: how does one quantify or define what “mental potential” or, on the opposite side of the spectrum, what “potential brainpower” is? As Kenneth Higbee wrote, “even if researchers could define mental potential, I doubt that they could measure it to determine what constitutes a person’s total potential. [also], even if they could define and measure mental potential, I doubt that researchers could define what it means to ‘use’ our mental potential, and that there would be any way to measure what percentage of the total we use.”

He believes that we do have more potential mental ability than we use, but believes the whole “10 percent” to be intellectually dishonest and useless. Inherent, unused mental ability is vastly different than “parts of our brain we don’t use.”

as an aside, even if you were to “tap” into that unused potential, nothing drastic will happen. you won’t wake up in a human farm resemblant of The Matrix.

LostInParadise's avatar

@drdoombot , Exactly what I was trying to say when I mentioned Occam’s Razor. If two proposals have equal explanatory power then you go with the simpler one, in this case that what appears to be real is real.

jackm's avatar

@LostInParadise
How is that simpler? I am not disagreeing with you, I just wanted to know your logic.

HGl3ee's avatar

@Grisaille good point. However in my response I never talked about the whole idea of humans only using 10% of their brain. Kenneth Higbee wrote from a personal stand point. At least from what I can see, being he wrote: “I doubt..”

I see the term using 10% of our brain as a generic term to describe that humans are capable of so much more but this “more” is unknown and something to be discovered. In saying we have 10% of our brains “discovered” while the other 90% is waiting to be “discovered” or used. It’s in no way factual by any means but as humans we try to put things into perspective even if it’s impossible.

Having something known is much more comforting then the unknown. Again this is all in my own opinion. I am not saying you are wrong in any way, just saying that it is just one of many opinions that are all possible because it is something we cannot prove.

Anything is possible. Above and beyond what we are capable of understanding. – LB

Shuttle128's avatar

@jackm The theory that contains the fewest assumptions is usually the most preferred. In this case, if the outside world did not exist, you would have to explain why it behaves exactly as it would if it was real, the mechanisms by which it introduced sensory data to you, and where the computational power to simulate a universe is coming from. It has more unsupported assertions than a real world so a real world should be most preferred.

The thing is, all of the outside world, whether real or not, requires computation. The real world requires (most likely) the least computation as it follows simple rules of physics propagating though time. A simulated Universe would require at the very least the same computational power as the Universe we live in now, if not more. The simulated Universe can be computationally reduced to the same computations as the real Universe. If a simulated Universe is computationally reducible to the same thing as a real Universe it follows that the less complicated explanation should be favored.

Grisaille's avatar

@ElleBee Kenneth Higbee is a doctor of philosophy and professor of psychology at Brigham Uni; I quoted him from one of his books on the mind and memory. He isn’t pulling this out of nowhere; he’s published hundreds or reports in professional journals and has conducted workshops throughout the world. If there was anyone qualified on speaking on neurology, memory and the way the brain functions and stores information, it would be him. Not subjective in the slightest.

The brain is a physical thing; mind, less so. The brain in itself is incapable of performing outside of itself – that is, it performs its processes as it has and will. There is no physical portion of the brain that lays dormant, waiting for it to be tapped into. There is nothing physical to discover about it, other than counting and mapping synapses, why and when.

The mind and memory, however, is a different conversation. It functions outside itself, almost.

Imagine, if you will, being able to view your “mind” as it were when you were ten years old. It would appear primitive and lacking in substance. Now imagine your present day “mind”, a whirling, sprawling mass of complexes, all interconnected to one another at various points. The difference between these is remarkable, but not because you’ve tapped into some power of the mind you were unable to do when you were ten. With growing knowledge of the functions of the universe, science, philosophy, politics, society, etc, it has grown; not broken through some imaginary wall. Continued knowledge will just expand it.

Your comprehension is not fettered to some physical barrier. When you have a “eureka” moment, it is you connecting pre-existing knowledge together – even if it is an idea that seems new, it is still rooted in your memories. What I’m trying to say is that there is no “untapped” portion of the mind – definitely not 90% of it – that is waiting to be claimed. Your mind works as a canvas – it started as a black, dark and, most importantly, endless place. As you started to learn letters, words, and images, they started to appear as dots of light on the canvas. As you began learning correlation between these items, they started connecting to one another. It grew and grew to what you call your mind today. A complex of memories.

Having something known is more comforting than dwelling in the unknown, I agree (thanks, religion). However, inventing unknowns to supplement the lack of certitude in modern mental prowess is even worse. When Higbee says that we have potential mental ability, he’s speaking not of some mystical, higher mind that can be achieved if we break into it. He’s speaking of compiling data into our mind, and that we all have the ability of improving memory, comprehension and coherence if we learn how to learn efficiently.

Saying “anything is possible” is very true; philosophy has taught us that there is no such thing as an absolute truth or an absolute falsehood, as either proving or disproving something complete is impossible. Also true is the famous “the absence of evidence does not equate to the evidence of absence.”

However, when the evidence runs contradictory to belief, then holding onto it becomes dangerous. The evidence is stacked against the “10%” theory, and, thus, can be safely discarded.

bennihan's avatar

nothing is real. perception is reality

Shuttle128's avatar

@bennihan If that’s the case then perception is real…..and if something is real, then the statement “nothing is real” is false.

mascarraaa's avatar

maybe its not real. maybe its all in our minds.
maybe..

Shuttle128's avatar

Then our minds must be real. Something has to exist whether the world is fake or not.

Jeruba's avatar

I can tell you that there’s stuff going on that I didn’t think of.

LostInParadise's avatar

A related question would be to ask how we know something is unreal. How do we know when we are seeing a mirage? How do we know that something is an optical illusion? I suppose it comes down to a matter of consistency.

There is an interesting related scene in the movie A Beautiful Mind about the mathematician John Nash and his struggle with schizophrenia. Nash decided not to take medication, because he felt it interfered with his creativity. He learned to live with schizophrenia. The scene that I am thinking of shows Nash viewing imaginary companions and dismissing them as unreal. That must be a strange experience, to see something that seems so real and to know at another level that it is a figment of your mind.

wundayatta's avatar

@LostInParadise Oh that’s easy! For example, this conversation is unreal! Totally!

mineown's avatar

R.I.P. Kurt Cobain

HungryGuy's avatar

You don’t. All that you perceive is sent to your brain from your senses. Your brain could be in a jar with your spinal cord interfaced to a computer running a high-def 3D simulation, and you’d never be able to tell the difference.

Response moderated
Nullo's avatar

Sight collaborates nicely with the rest of our senses,

Moegitto's avatar

Perception is a S.O.B. Some Blind people have the ability to use their other senses to perceive the environment around them (look it up, it’s real.) The way they see life is different from ours because we depend on sights. Even dogs (mostly mastiffs) do this when they get older because they go blind easy, they then start to use smells and the textures they walk on to get around. i bet most dogs that go blind walk into walls!!

Nullo's avatar

We have no reason to suspect that what we see isn’t real. Ultimately, it makes no difference.

flutherother's avatar

Grass is green and we all experience a similar sense of ‘greenness’ when we look at grass and so we agree on the reality of green grass. The experience of ‘greenness’ is common to all humans and results from the way our eyes and our minds have formed in the course of evolution and cannot be said to be an objective reality. There is the reality of the world as we experience it which overwhelms us and there is the ultimate reality of things as they really are which we know little of. The world can be considered a dream, but within this dream there must be something real though we may never find it.

tigress3681's avatar

We don’t know for sure that what we are percieving is real. We do know that there is an objective correlation between viewers, although two people viewing the same objective event may see different things depending on their experiences/viewpoint/visual acuity. That said, welcome to philosophy 101.

josie's avatar

There are really only two possibilities. Your brain is making it all up, or you are experiencing reality pretty much the way it is.
So, which assumption is the most likely? Which assumption gives you the best shot at a happy life?
What evidence exists that all of your experiences are an illusion? How does this evidence refute the obvious conclusion that your experiences are real?
Seems pretty simple to me.
Unless I am not really here at the same time you are imagining that I am here.- :)

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