There must be a dozens of threads on similar questions about realism and perception. Setting aside the plausibility of the claim. The salient question I have on this is, why does it matter? If the world is only here when you are getting on with things and perceiving it, isn't this the important part? Like idealism, the notion is of no practical consequence as we go about our lives.

So if I am unconscious, the world disappears? Does this mean that if I am unconscious and my girlfriend is conscious, it still exists? Or is the world she sees a different world to the one I see?

Or is it only the case that the world vanishes if no one at all is looking?

Or is this arguing from solipsism?

I would like to see the logical and epistemic arguments laid out for the reason for believing in the existence of the world. — Corvus

If you are typing this and asking others for opinions, aren't you committed to the existence of the world?

I am interested in seeing the logical reasons for believing in existence of the world or objects without perceiving them. It is not about the actual world or objects, but the thinking process for the reasons of our beliefs in existence.

Are our beliefs in the existence of the world or objects based on some logical reasoning? or is it just all groundless, habits and customs to believe in these things?

If you are typing this and asking others for opinions, aren't you committed to the existence of the world? — Tom Storm

As I am typing this, I am perceiving my surrounding objects and the world around me vividly. So yes, I am believing in their existence for sure.  But I don't have any reasons to believe in anything else in this world I am not perceiving.

If I understand your point correctly I’d say we have far more reason to believe in the objective existence of the world than not. The onus is on the person that says it isn’t real, a simulation etc.

I have been asked by ↪Ludwig V in another thread, if I believed in the existence of the world, when I am not perceiving it. — Corvus

Is it possible for you to be not perceiving the world while you are still alive? Would this be when you are asleep? But don't things still wake you up? Are you not in some way perceiving the world even when you are asleep?

Once, when I was lucid dreaming, meaning aware I was asleep, I took a picture with my smartphone to see if when I awoke it would be on my phone's gallery.

It wasn't.

But I definitely took a picture and left a message. It remains in my mind, and now in yours. But neither of us can access it physically, here and awake, that is. So what does that mean?

I do believe in the existence of the cup when I am perceiving it, but when I am not perceiving it, I no longer have a ground, warrant or reason to believe in the existence of it. — Corvus

I would like to see the logical and epistemic arguments laid out for the reason for believing in the existence of the world. — Corvus

Perception is not based on logical inference. So, if your reason for not believing in the existence of a cup because you're no longer perceiving it, then your reason is not better or more sound than believing in its existence while it's in front of you. And the reason for this is well-articulated by many metaphysicians. You could be mistaken in your perception.

If you're looking for the logical grounds for believing in the existence of the world, then what better way than your own thoughts in refusing to believe. Someone, like you, who refuses to believe in objects not existing is the best, surest reason for believing there's something. You exist.

If I understand your point correctly I’d say we have far more reason to believe in the objective existence of the world than not. The onus is on the person that says it isn’t real, a simulation etc. — Captain Homicide

So what are your reasons and proofs for believing the world exists, when you are not perceiving it? What is the ground that says, something isn't real? How do you tell something is a simulation, rather than real?

Is it possible for you to be not perceiving the world while you are still alive? Would this be when you are asleep? But don't things still wake you up? Are you not in some way perceiving the world even when you are asleep? — Metaphysician Undercover

When one is alive, and perceiving the world, of course, one believes in the existence of the world, because one has the ground for believing in the existence of the world.  But when one is dead, or asleep, there is no longer perception for the individual.  Therefore could it be the case that there is no reason for the individual to believe in the existence of the world? Would you say that one should believe in the existence of the world, when one is dead or in deep sleep?

It wasn't.

But I definitely took a picture and left a message. It remains in my mind, and now in yours. But neither of us can access it physically, here and awake, that is. So what does that mean? — Outlander

It sounds like you had a real vivid dream, which felt to you like real life happening. When you woke up, and tried to verify if it was a real life event or not, it was just your dream event. So, could it mean that we might all be dreaming right now? How do we tell the dreams from the real world, or real life events from the dream events?

Perception is not based on logical inference. — L'éléphant

So what are our perceptions based on, if not on the logical inference?

If you're looking for the logical grounds for believing in the existence of the world, then what better way than your own thoughts in refusing to believe. Someone, like you, who refuses to believe in objects not existing is the best, surest reason for believing there's something. You exist. — L'éléphant

I don't have to refuse or agree to believe. But could I not just say I don't have a reason to believe, when there is no reason to believe? I don't deny my existence when I am awake and perceiving the world, because if I didn't exist, then the perception would be impossible.

But then again, when I am asleep, I don't have a ground to believe that I exist. Do you have reason to believe that you exist, when you are in deep sleep? If yes, what are the reasons for your belief? How can you think about the reasons that you exist while in deep sleep?

To see what other folks think about this issue, I have opened this thread asking what is your reason to believe in the world, when you are not receiving it? — Corvus

Occam's razor, for me. It is a simpler model of the world that the world always works one way, than a model of the world that it works one way when I'm looking and another way when I'm not looking.

My answer to that question was, when I am not perceiving the world, there is no reason that I can believe in the existence of the world. I may still believe in the existence of the world without perceiving it, but the ground for my belief in the existence is much compromised in accuracy and certainty due to lack of the warrant for the belief. — Corvus

Corvus, I want to share with you some notes from Kelley Ross, when he finished his dissertation. My aim is not to force you to believe on the existence of the world, but to see another prospective in its prism. Ontological Undecidability

Ross states:

A thing in itself is in fact the object = x which stands outside of our knowledge, over and against our representations, and which in some way we suppose corresponds to the knowledge that we have of it. That would be the straightforward Cartesian view of things. In Kant's theory, however, all those functions of an "object" have been taken over by the object-forming functions of synthesis, and Kant's own awareness of this is evident enough in his conclusion that things in themselves are not known by us and so do not, in any familiar fashion, correspond to our representations after all.

He continues:

It is essential, therefore, that just how "realism" and "phenomenalism" are going to be distinguished from each other be pinpointed, both in Kant and in the larger picture of knowledge. Let me do this now by saying that the defining criterion for the difference, and the origin and essential feature of the whole matter, is as a question of existence: that we are all distinct, separate, and independent in existence from the things (except the body) that we know through perception. They can exist when we don't; and we can exist when they don't; and our veridical perceptions are supposed to represent them.

But he admitted:

The difficulty of phenomenalism, where "the representation alone must make the object possible," is that this feature of existence is easily lost. Indeed, if what phenomenalism means is that the reality of an object is exhausted by its features in the representation of a subject, then it is hard to see how this differs from solipsism or subjective idealism

But, if we are not directly acquainted with the real objects of experience, and they exist, then the real objects of experience are separate from us.

Corvus, I want to share with you some notes from Kelley Ross, when he finished his dissertation. My aim is not to force you to believe on the existence of the world, but to see another prospective in its prism. Ontological Undecidability — javi2541997

Hello Javi.  Thanks for your quotes from the article, and points.  It is very helpful, and interesting. It is interesting that the author of the article sees Kant's Thing-in-Itself as objects beyond human understanding.  Once upon a time in the past, I too, was looking at the concept that way.  

Would it make Kant an idealistic dualist?  The dualist who thinks that there are two different worlds i.e. Phenomena and Noumena. It is also an idealistic world view because the world is in the mind of the perceiver i.e. without the perceiver, the world doesn't exist?  Would this be the right interpretation for Kant?

But, if we are not directly acquainted with the real objects of experience, and they exist, then the real objects of experience are separate from us. — javi2541997

The point of the OP was not that I don't believe in the existence of the world when not perceiving it, or trying to deny the existence of the world as such. But I was trying to see what the logical grounds are for our belief in the existence of the world.

This epistemic problem has been dogging the philosophers from the ancient times, and in the modern times Hume and Kant as well. They have been propounding and analysing the issues in their work extensively. But I was wondering, if the old problems regarding the scepticism have been sorted out with some concrete resolutions in recent times and even now as we are discussing the issue in here, or is the problem still hanging in the air with the same controversies as long before in the history of Philosophy from the ancient to the early Modern times.

Is our belief in the existence of the world based on some logical evidences and reasonings based on the perception?  Or is it by inductive reasoning? Or would it be just habits, customs or animal instincts?

I would like to see the logical and epistemic arguments laid out for the reason for believing in the existence of the world. — Corvus

You are correct in that you have no immediate reason a posteriori to believe in the existence of the world in the absence of perception. It is still the case you have mediate reason to believe a priori, in the existence of the world, iff you’ve a set of cognitions from antecedent perceptions. And it is impossible that you do not insofar as you’re alive and functioning, so…..

The logical and epistemic arguments for a priori justifications has been done, and is in the public record. They serve as explanation for not having to re-learn your alphabet after waking up each morning, given that you already know it.
————-

Is our belief in the existence of the world….. — Corvus

Everydayman doesn’t bother himself with believing in so obvious an existence, any more than he bothers himself with doubting the non-existence of it.

For the philosopher or the scientist, it is quite absurd to suppose either of those merely believe in that existence the ignorance of which, for them, is impossible.

Which begs the question….who else would even wonder about it?

You are correct in that you have no immediate reason a posteriori to believe in the existence of the world in the absence of perception. It is still the case you have mediate reason to believe a priori, in the existence of the world, iff you’ve a set of cognitions from antecedent perceptions. And it is impossible that you do not insofar as you’re alive and functioning, so….. — Mww

But can the world be the object of a priori knowledge? When you say precedent perception, could it be memory? Doesn't memory tend to be unreliable for qualifying as a ground of infallible knowledge or justified belief?

The fact that someone is living and functioning doesn't mean that the folk have infallible ground for the existence of the world, does it? All he might be interested in his mind could be the football results on TV, or his stag night plans with his pals in coming weekend. These are the people whom Hume calls the "vulgars" in his Treatise. They would not even understand what the question or issues are with the scepticism regarding the external world.

As you said, most folks in ordinary daily life don't bother or care about the reasons to believe in anything. They just do.

Everydayman doesn’t bother himself with believing in so obvious an existence, any more than he bothers himself with doubting the non-existence of it.
For the philosopher or the scientist, it is quite absurd to suppose either of those merely believe in that existence the ignorance of which, for them, is impossible.
Which begs the question….who else would even wonder about it? — Mww

Some folks seem to think, why is this issue important or significant? I think it is interesting and significant because perception is perhaps the most important thing in leading a meaningful and trouble free life. Not just for human beings, but even for the animals on this earth.

Suppose that if a dog cannot tell the difference between a cat and tiger, and when he saw a tiger, if the dog chased the tiger barking thinking it was a cat, then he would be eaten fast by the tiger, and no longer exist. But the matter of fact is that, even a dog would perceive the tiger, and know the imminent danger, and run away as fast as he could hiding for his own safety.

For human beings, if you drive a car when you are not perceiving the road ahead of you, believing that it exists even if you are not perceiving it, and keep on racing away into a river, then that would be a disaster. When you don't perceive the road ahead of you, you simply say to yourself, you no longer have reason to believe there is a road ahead of you, and get out of the car, and take a taxi home. Wouldn't it be a more rational thing to do?

Cheers. I wish I could keep arguing and debating with you on this pretty interesting thread, but my knowledge of this topic is limited, and I am just a wannabe philosopher. I personally think that other members are more capable of answering your questions, or at least post more suitable answers. I think the website of Kelley Ross is good for learning, but it is true that it has complex paragraphs to understand. The link I posted below comes from an essay that has never been published, sadly. I don't understand why because it seems so interesting what Kelley Ross post there, and didactic with examples and explanation.

Would this be the right interpretation for Kant? — Corvus

Regrading this question, Kelley Ross states: The question then is why the thing in itself remains in the theory. To subsequent generations it has seemed that Kant ends up with a precarious, paradoxical, and perhaps even incoherent dualism between things in themselves and the phenomenal objects produced by synthesis. The thought here, however, is that Kant was right to retain his dualism. It is one indication of how delicate is Kant's balancing act in the equation of "transcendental idealism" and "empirical realism" that it is the "realism" of the latter that even those sympathetic with Kant have trouble taking seriously.

As I am typing this, I am perceiving my surrounding objects and the world around me vividly. So yes, I am believing in their existence for sure.  But I don't have any reasons to believe in anything else in this world I am not perceiving. — Corvus

If you want to be precise about it, as you are typing, what you perceive takes the form of a temporal flow. The world around you and your surrounding objects are not perceived simultaneously but in temporal succession. It is only via recollection that what has immediately passed is retained such that it can appear as co-existent with what is immediately presented. to you. If we had to rely only on what we are actually perceiving in this moment with no access to memory, we would not recognize objects and patterns. The world ( including the ‘I’) would be a meaningless series of isolated ‘nows’ with no sensible content. There could be no persisting objects nor processes. Your belief in the ‘simultaneous’ world around you while typing, and your belief in your own immediate existence, is no more justifiable that the belief in anything else.

On the other hand, one could argue that what is irreducibly valid is the temporal structure of retention, the present, and anticipation, forming a moving zero point of perception. There is indubitable evidence for a past as well as a present, because the past persists inside of the present. If there is is no perceived past there is no perceived present. We could call this moving zero point a transcendental ego.

Honestly though, this is the kind of "philosophy" that feels affectatious. Loaded question that doesn't lead to any real wisdom. — Vaskane

But didn't even Neitzsche believed that the ultimate knowledge of the true reality was impossible to achieve? In that sense, wasn't he also a sceptic? Although his Philosophy is more tuned for Value, Freedom and Taste oriented, would you not agree that you can only come to true value, freedom and taste via the true knowledge? In that sense, you must define what truth is, and also have the verified ground for your belief that your knowledge of the world is free from error, prejudice and uncertainty?

Not perceiving the world would require you to be rid of ALL of your experiences of it. Even when an artist is between the Apollonian dreamland and the Dionysian intoxication, and they are freed from all the contradictions inside of themselves during their creative passions, they too still perceive the world, while in the zone of their own universe. — Vaskane

How do you prove that the artist is not dreaming or imagining on the contradictions, perceived world and universe?

You can only stop perceiving the world in death alone, so yeah, you stop believing then too because you're dead — Vaskane

But you don't have to die to stop perceiving the world or not to have any reason to believe in the existence of the world. You can have a good night sleep instead of death, and you can have all that with some sweet dreams as bonus while in sleep too. Death sounds too morbid and needless if you are not 100++ years old yet, doesn't it?

The link I posted below comes from an essay that has never been published, sadly. I don't understand why because it seems so interesting what Kelley Ross post there, and didactic with examples and explanation. — javi2541997

I think it is a quite good article on Kant. Lately I wanted to read some new and different commentaries and views on Kant, instead of the traditional interpretations on him. Seemingly there are hundreds and thousands of commentaries and papers on Kant's philosophy from the time after Kant's death to even now. It just tells us how influential his philosophy has been.

Regrading this question, Kelley Ross states: The question then is why the thing in itself remains in the theory. To subsequent generations it has seemed that Kant ends up with a precarious, paradoxical, and perhaps even incoherent dualism between things in themselves and the phenomenal objects produced by synthesis. The thought here, however, is that Kant was right to retain his dualism. It is one indication of how delicate is Kant's balancing act in the equation of "transcendental idealism" and "empirical realism" that it is the "realism" of the latter that even those sympathetic with Kant have trouble taking seriously. — javi2541997

It seems an interesting view on Kant. I am not an expert on Kant myself, but am interested in learning more on his philosophy with on-going readings and discussions on the topics.

But didn't even Neitzsche believed that the ultimate knowledge of the true reality was impossible to achieve? In that sense, wasn't he also a sceptic? — Corvus

Nietzsche didn’t ‘doubt’ ultimate knowledge of a true reality, which is what skepticism entails. Rather, he considered that quest a nihilistic aim, an attempt to stifle and freeze living becoming. For. ietzsche, question s like whether a. external world can be justified misses the point, which is the world is not a container with furniture, but a process of endless transformation.

The world ( including the ‘I’) would be a meaningless series of isolated ‘nows’ with no sensible content. Your belief in the ‘simultaneous’ world around you while typing, and your belief in your own immediate existence, is no more justifiable that the belief in anything else. — Joshs

I have read about this from a neurology paper, and was agreeing to its point fully. But then my memory is vivid and fresh enough to catch up that momentary pasts and render into the legitimate perception. In that sense there are the parts of memory which could be regarded as perception. It is only when long time interval has passed, the contents of memory goes stale or fade away resulting in total loss of the past cognitive perception.

On the other hand, one could argue that what is irreducibly valid is the temporal structure of retention, the present, and anticipation, forming a moving zero point of perception. We could call this zero point a transcendental ego. — Joshs

This sound like the mental state some Buddhists try to achieve in their meditation practices. I read that they try to achieve selfless mental state by focusing on the internal concepts or the teachings of Buddha in the text.

Hume would say that you are looking through the wrong end of the telescope when demanding a warrant for accepting the existence of the world:

Here, then is a kind of pre-established harmony between the course of nature and the succession of our ideas; and the though the powers and forces by which the former is governed be wholly unknown to us, yet our thoughts and conceptions have still, we find, gone on in the same train with other works of nature. Custom is that principle by which this correspondence has been effected, so necessary to the subsistence of our species and the regulation of our conduct in every circumstance and occurrence of human life. Had not the presence of an object instantly excited the idea of of those objects common conjoined with it, all our knowledge must have been limited to the narrow sphere of ou memory and senses, and we would never have been able to adjust mans to ends or employ our natural powers either to the producing of good or avoiding of evil. Those who delight in the discovery and contemplation of final causes have here ample subject to employ their wonder and admiration.

I shall add, for a further confirmation of the foregoing theory, that as this operation of the mind, by which we infer like effects from like causes, and vice versa, is so essential to the subsistence of all human creatures, it is not probable that it could be trusted to the fallacious deductions of our reason, which is slow in its operations, appears not, in any degree, during trhe first years of infancy, and , at best, is in every age and period of human life extremely liable to error and mistake. It is more conformable to the ordinary wisdom of nature to secure so necessary an act of their mind by some instinct or mechanical tendency which may be infallible in its operation, may discover itself at the first appearance of life and thought, and may be independent of all the labored deductions of the understanding. — An Inquiry Concerning Human Understanding, David Hume, Section 5

From this point of departure, the skepticism you are entertaining requires embracing a world of experience before withdrawing from it as a thought experiment. The absence encountered is the result of your subtraction.

Rather, he considered that quest a nihilistic aim, an attempt to stifle and freeze living becoming. — Joshs

"a nihilistic aim"? Doesn't it sounds like a contradiction? When nihilist has aim, doesn't he stop being a nihilist? What was the reasons for him doing that?

Hume would say that you are looking through the wrong end of the telescope when demanding a warrant for accepting the existence of the world: — Paine

I wasn't demanding a warrant for accepting the existence of the world, but was asking the reasons for your accepting the existence of the world. i.e. Why do you believe the world exists, when you are not perceiving it?

Because it is more coherent and is better supported than the alternative of nothing existing absent us. There is more to evidence than continuous perception of a thing.

Heck, the world might not be continuous, but even claiming this stops way short of saying that nothing exists. Of the latter claim, we have virtually no evidence.

Wouldn't it be like saying that the earth looks more flat than round, so it must be flat. It looks like the Sun is rotating the earth, so the Sun is rotating around the earth?
This was what the ancient and the medieval people believed and supported, and anyone saying against it was punished by law too.

But it has been turned around by Copernicus and Galileo totally and incredibly. So what looks seemingly like the case, and supported by the majority is not always the truth.

but was asking the reasons for your accepting the existence of the world — Corvus

Hume is saying that reason does not do that acceptance in the sense of a series of formal statements or a priori set of conditions. The belief in the world's existence is prior to any doubt.

Hume is saying that reason does not do that acceptance in the sense of a series of formal statements or a priori set of conditions. The belief in the world's existence is prior to any doubt. — Paine

Could you prove why the belief in the world's existence is prior to any doubt on behalf of Hume? Do you believe he is justified in saying that? i.e. why reason doesn't do that acceptance in the series of formal statements or a priori set of conditions - I think we need detailed elaboration on this assertion.

But can the world be the object of a priori knowledge? — Corvus

No, but irrelevant, because the question was, can it be believed the world exists without perception of it.

When you say precedent perception, could it be memory? — Corvus

Ehhhh….that’s for the psychologist. For the metaphysical philosopher, perception is mere appearance, an as-yet undetermined affect on physiology by something, and from which there is no memory as a determined thing.

Doesn't memory tend to be unreliable for qualifying as a ground of infallible knowledge or justified belief? — Corvus

Every belief is justified, and no empirical knowledge is infallible, so it would seem memory drops out of consideration for either. A priori knowledge, on the other hand, is infallible, but does not obtain its certainty from memories of things, but from the necessity of principles.

But we’re talking about believing in the existence of the world, which already presupposes it. We should be discussing belief in the continuation of such existence, rather than existence itself.
————-

I think it is interesting and significant because perception is perhaps the most important thing in leading a meaningful and trouble free life. — Corvus

In which case, we shall always disagree, in that you are doing empirical anthropology and I’m doing cognitive metaphysics. This irreconcilable dichotomy reduces to the impossibility for qualitative judgements such as meaningful and trouble-free life, being derivable from ontological predicates, such as existence.

Now, there is the domain or paradigm where the subjective condition is pleased or disturbed….certainly a qualitative judgement if there ever was one….given the mere sensation of something, but with respect to the original query, re: can the existence of the world be believed without perceiving it, these judgements, being purely aesthetic in nature, have no say regarding objective necessity.

if you drive a car when you are not perceiving the road ahead of you….. — Corvus

….then you are not driving the car. You’re merely the payload in a projectile.

Wouldn't it be like saying that the earth looks more flat than round, so it must be flat. It looks like the Sun is rotating the earth, so the Sun is rotating around the earth?
This was what the ancient and the medieval people believed and supported, and anyone saying against it was punished by law too.

But it has been turned around by Copernicus and Galileo totally and incredibly. So what looks seemingly like the case, and supported by the majority is not always the truth. — Corvus

It's rather the opposite, funnily enough.

The world looks and feels flat, but there is much more evidence to support the claim that it is round, but most of the evidence we use to support this claim comes from experiments which go beyond immediate conscious perceptions.

So, your own example is an argument against your own OP.