Yeah I think I get what you are saying too, that in terms of total content that is existing in the real world and displayed in the illusory world at one time, (3) can have less total content than (2). But I don't think that "less content in the objects of explanation" translates to "lesser complexity of the explanation". I illustrate with an example.

I observe a house from the front side. Then I circle around to check that all 4 sides are fully built. I observe that no wall is missing. Kinda like this. I can draw 2 explanations.

(1) There are really only 2 walls existing, and a swift house builder just moves the 2 walls around as I circle around, to make it look like there are 4 walls.
(2) There are 4 walls.

One could argue that explanation (1) has less content in the objects of explanation (ie 2 walls + 1 builder as opposed to 4 walls). Yet clearly explanation (2) is the simplest in terms of explanation.

So if you want to establish burden of proof as an epistemological principle for metaphysical questions, you'll have to justify the connection between the rule and metaphysical reality. — Echarmion

Sure. Aside from mathematics and pure logic, we never reach certainty for any other sciences. In all other sciences (metaphysics and others), the accepted position about a topic is the one that has not yet been refuted. We say that the position stands, that it becomes the prima facie, and that the onus of proof is on the other side. It is a good alternative to remaining agnostic about everything merely on the grounds that we do not reach certainty. Maybe we can afford to remain agnostic on some topics, but not all. See next paragraph as an example.

The problem is that this false perception may very well be normal, even unavoidable, for humans, and therefore your previous arguments do not work. — Echarmion

This topic of whether all perceptions are false or some are true, is a good example where we cannot afford to remain agnostic on the grounds that both hypothesis remain possible. We gotta live. We gotta pick a side. Enters the Prima Facie approach as per above.

So what about the colour red? Is it real or imaginary? — Echarmion

Hmmm.... That's a tough one. It's almost worthy of its own discussion. For now, I say real; as we cannot conceive something we have not experienced in the past. E.g. a blind man born blind cannot conceive the colour red.

How would that be possible? Do you imagine there to be some actual rulebook hidden somewhere that is the "object" you could base morality on? The question of morality is "what should I do". How is that in any way connected to objects? — Echarmion

The objective basis to ethics is values, ie that some things are good or bad in reality. E.g. I should do this because it is objectively good.

Another one would actually be epistemology itself. Because if epistemology is about discovering the "objective nature" of the universe, then the truth criterion for that cannot be "accordance with objective nature". That'd be circular. — Echarmion

Siding with Aristotle, the foundations of epistemology are first principles called the laws of thoughts. These laws are Deductive Reasoning (aka logic), Inductive Reasoning (aka stats), and Abductive Reasoning (aka Parsimony). As first principles, they are not founded on any other premises.

Whether or not you prefer to reserve the term "reality" for "objective" or "metaphysical reality" doesn't change whether or not the latter is connected to physics. — Echarmion

It does. Let me try again another way. We perceive a physical object. Either that object is real or not. If real, then we made a claim about metaphysics. If not real, then the explanation is the existence of a false perception. Then we still made a claim about metaphysics, namely that this false perception is real.

if you have a collection of random thoughts, some of those could just happen to conform. — Echarmion

Good point. Let me try again: Knowledge is achieved when the thoughts are true and justified, and correct justification must follow the laws of thoughts.

It seems to me this statement can be viewed in one of two ways. (1) You are either making a claim about how we already do things (i.e. using witness testimony to corroborate facts), or (2) or you are concluding from your argument that philosophical realism holds. — Wolfman

Both. The witness testimony uses the PUP to determine the most reasonable story about the case. And that same rationale is used to determine the most reasonable claim about metaphysics.

Your premise already assumes that external objects exist; it's just that whether something is objectively real or not depends on the number of people who saw it. But you haven't even established that external objects exist in the first place — Wolfman

External objects must exist for us to have true or false perceptions of them. Also I am fairly sure Hume did not question the existence of external objects; and was only skeptical about their true nature.

This debate would have been over hundreds of years ago if it were that easy. — Wolfman

Unless all those debaters used that similar line of circular reasoning. :wink:

Let's call the two hypotheses as so: (1) for world as we perceive it; and (2) for brain in a vat.
One formulation of Occam's Razor is: Entities should not be multiplied without necessity.
In hypothesis (1), the entities are: A real world which we perceive.
In hypothesis (2), the entities are: A real world which we don't perceive + an illusion of the world we perceive, created by a machine in that real world.
Hypothesis (1) is composed of fewer entities, and is therefore simpler.

Now you argue that it is easier in (2) to create the illusory world, than in (1) to create a real world. But this omits the fact that in (2), a real world also exists, which includes the machine that creates the illusory world. And appealing to the Principle of Sufficient Reason, an effect necessitates a sufficient cause. The machine containing the information for the illusory world must exist in a world that is at least as rich in information.

Haha! True that.

I am not a fan of "burden of proof" type arguments outside of a legal context. While I think the general rule that the one who advances a claim is obligated to provide justification is a fine one, it's a rule of debate, not a law of (meta-)physics. I am repeating myself here, but there is no reason to suppose that the world cares about the burden of proof. — Echarmion

But the point of (sincere) debate is to find truth. Proper rules of reasoning and debate (which includes burden of proof) is part of epistemology. You might as well say that the objective world does not care about epistemology as such, which is true, but would miss the point that the function of epistemology is to know the objective world.

A Hallucination is a specific way in which one persons perception differs from the perception in others in defined, pathologic ways. Hume's scepticism goes deeper than that. It's not about individual mistakes but about whether humans are at all equipped, sensory or otherwise, to gain knowledge about metaphysical reality — Echarmion

That's fine. Instead of "hallucination" let's called it "false perception", for which "false" means "not in conformance with reality".

For any given ability to observe, one can make up teapots that fall just outside of it. — Echarmion

We (at least I) may have lost track of what the original point was here. If that's okay, we can leave this tangent as is.

Sure, but then your statement "reality implies objectivity" reads "reality implies external reality", which is wrong, as there are obviously internal realities. — Echarmion

I don't believe so. There are only 2 categories of being in that sense: real and imaginary. E.g. a horse is real, a unicorn is imaginary. By "internal reality", I am guessing you actually mean "imaginary" which is the alternative to being real.

[...] So even if metaphysics would be impossible, there'd still be truth. [...] — Echarmion

I still challenge this claim. Ethic is only properly speaking a science if it is objective; which means that goodness exists in reality. But if no goodness in reality, then no ethics. Similarly, there is no such thing as "physical reality" if we can know nothing about reality. Even if the physical is the result of a false but universal and consistent perception, we are then still claiming that this false perception exists in reality.

Which is good, if you think that thoughts construct reality. Do you? — Echarmion

Of course not. But true thoughts are thoughts which content conforms to reality. And true thoughts are possible only if they follow the laws of thoughts.

Which would be easier or, if you prefer, more parsimonious: an illusion of a universe or an actual universe? The answer to that question is, according to none other than the Principle of Parsimony: an illusion of a universe is simpler than an actual universe. — TheMadFool

Wait why is the illusion the simpler explanation? In both cases, true or false perception, some sort of universe must exist for us to have a perception of it. But in the illusion case, we must posit the state of having an illusion on top of having a universe. Then to be picky, we must also posit an explanation for why the illusion is so structured and consistent (as opposed to continuously changing). With that, I would say the actual universe is the simplest explanation.

Given the context of my last post, it should be pretty clear that I'm explicating Hume's views, not mine own. You should abide by the principle of charity instead of cherry picking and coming back with this kind of response. — Wolfman

Well I thought that since you were defending Hume's position, you agreed with him. My bad for assuming. Bonus, I didn't know about this Principle of Charity. That's a good one.

As for Hume's claim: If he claims something drastically different than what I described in the OP, then we can discard it. It doesn't make the PUP any less valid on its own. Now for fun, we could try to examine Hume's true claim, or else leave it there. Up to you.

Hello.
Fortunately, we have principles of reasonableness like the Principle of Parsimony, to keep us grounded in common sense, and prevent us from getting lost into too many "What if" questions.

So if I understand correctly, "belief" in our common language is a catch-all term which could mean either "guess", "estimate", "supposition" or "opinion", and as it is less clear than the other terms, it should be avoided. I can accept that. Can't deny that clearer is better.

I'm not sure I understand your point. Let me try to summarize where I think we are.

Problem 1: Either some perceptions are true, or else all could be an illusion.
Solution 1: Appealing to Principle of Parsimony, the former is more reasonable than the latter. It thus becomes the Prima Facie.

Problem 2: Some perceptions are true, but we know some are not (e.g sometimes my eyes fail me when I've been drinking). How to validate the perceptions?
Solution 2: Appeal to the Principle of Universal Perceptions. If the perceptions pass the PUP, then the belief that the perceived object is real becomes the Prima Facie.

Is there a problem still pending?

YES. [...] — unenlightened

Well I am genuinely impressed. Nevertheless, this lack of trust, of assuming dishonesty until proven otherwise, is unreasonable. It fails the Presumption of Innocence. And I still maintain that most scientific demonstrations cannot be replicated by most people. If a cancer expert diagnosed you with cancer, would you spend the time to replicate the test yourself prior to going for treatment?

It comes to the same thing. Subjects can only know they perceive the same thing by communicating. — unenlightened

This also applies to some scientific tests such as testing new painkillers. Anyways, I'll do you a solid. Let's add the condition that the PUP is valid as long as the subjects are honest.

Here's one you can do yourself on your next holiday. [...] — unenlightened

This demonstration presupposes that the sun is far away from the earth. Flat Earthers would disagree. :razz:

You could as well have said "Hume says this, but clearly it is absurd, therefore he is wrong". — Echarmion

Not necessarily wrong. It just means he has the onus of proof. Absurd, common sense, reasonable, status quo, all these are terms which serve to establish who has the onus of proof. Once the onus of proof is fulfilled, then the claim stands, even if it is absurd.

Oh that's clever. So you get to set the status quo and then get to ask everyone for proof? — Echarmion

I don't set the status quo. I discover it by experience. If you want to be formal about it, you could survey what most people believe about hallucination and the normal. My money is that hallucinations are not seen as normal.

the teapot is too small to be revealed even by our most powerful telescopes. — Echarmion

Practical limitation does not entail that a thing is theoretically unobservable; unlike spirits for example.

Dictionary definitions are not arguments. That's how the term is generally used. Hume essentially questioned whether that use was actually correct. — Echarmion

My discussion, my rules. By objectivity, I mean "external reality" as per the dictionary, and that's how it will be used in this thread. :cool:

I don't think that those are the two only options. When discussing metaphysics a "true agnostic" position exists, i.e. there are simply things we can't make reasoned statements about one way or another. — Echarmion

Unfortunately, if you don't make metaphysical claims, then philosophy is impossible: Metaphysics is the science of what is real. If no knowledge of reality, then no truth (defined as conformance to reality), then no philosophy (defined as search for truth).

And actually... I just realized that the Principle of Parsimony is nothing but Abductive Reasoning, which is a fundamental law of thoughts.

Precisely. A rainbow of wisdom.

we can only perceive perceptions — Wolfman

So you claim that when we perceive an object, it is never the object in reality. And why would that be? If it looks, sounds, and feels like a duck, is it not reasonable to believe it is in fact a duck, until given a reason to believe otherwise?

Hello.

This is risible. — Banno

Give it time. It will grow on you.

I think you are inconsistent. If you claim that all subjects for the PUP can lie, then all scientists can also lie. How do you know the Earth is round? Did you conduct the demonstrations yourself, or do you rely on the claims of scientists?

Regardless, this is a misunderstanding about the PUP. As described in the OP, it states that "if a large majority of subjects perceives the same object, then [...]". It says "perceives", and not "claims to perceive".

"common sense" won't fly in a serious discussion. — Echarmion

I cannot agree with you there. Have you heard of the "absurd"? Reductio Ad Absurdum? All valid philosophical terms which criteria of judgement is common sense or common life experience.

You have to actually give reasons why it's "not normal" to hallucinate. — Echarmion

No sir. The onus of proof is on he who disrupts the status quo, and the status quo is that it is not normal to hallucinate.

For example, one might say that statements of existence or nonexistence about an object which is defined as unobservable are equally meaningless. — Echarmion

How is a teapot unobservable?

The problem Hume brings up is exactly that there seems to be nothing connecting reality (the things we experience) and objectivity. — Echarmion

Are you confusing the terms objectivity and subjectivity perhaps? Objectivity is defined as "external reality". Source

Philosophy isn't necessarily concerned with predictions. Epistemology, for example, is concerned what we can know, not what we will know. — Echarmion

True. I should have said that both science and philosophy aim for truth, which is conformance to reality.

But regardless of it's origin, the principle must stand for itself. — Echarmion

As previously mentioned, it is defended by the fact that the alternative method (that more complex explanations are more reasonable until proven false) leads to a reductio ad absurdum. Can't prove that invisible unicorns don't exist? Then they exist. And please don't ask me to defend the reductio ad absurdum principle, because we will then have a case of infinite regress.

This is definitely a tangent, but... let's do it.
I think I have a clear enough understanding of the distinction between belief and guess, supposition, and estimate. But what is the difference between belief and opinion? Genuinely asking.

on Hume’s view, there is a problem with how perception operates in the first place. — Wolfman

What problem would that be, that is not covered by the PUP?

And you don’t do this by appealing to the very system he says is flawed — Wolfman

The Principle of Parsimony is flawed? Why is that?

Something that might help in general: The first line of the OP on Hume merely served as an introduction to present the PUP. I am not really looking to refute a claim by Hume, but to determine if the PUP is valid.

Hello.
If I understand your post correctly, you say the PUP fails against radical skepticism, because the explanation of collective hallucination already presumes some things about reality, such as the reality of other subjects, where as the evil demon theory is more radical and makes no presumption about reality (except for the existence of said demon).

This is true. But although outside of the PUP, the evil demon theory also fails the Principle of Parsimony (which falls under rationalism and not under perceptions) which the PUP is also based on, because positing the existence of an evil demon is more complex than not.

I know that people lie — unenlightened

The fact that is it possible for people to lie does not count against the PUP. It is like saying that the scientific method is flawed because scientists who apply it can always lie about the results.

I will trust my eyes [...]
I know that [...] people see what they want to see — unenlightened

Don't these two sentences contradict? Unless you say you are above the second claim; and indeed, that does sound arrogant :joke: .

people conform. — unenlightened

This is true, and we must take it seriously. Fortunately, it can be controlled by doing things like a double blind test, etc.

So...your point is? — Frank Apisa

That I think you are applying the PUP when you say you are more inclined to pick scenario (1) over (2). We are in agreement that reasonableness does not give certainty, but it is powerful enough to tip the scales.

Now...the answer I would much prefer. Neither! I do not do "believing"...by which I mean I NEVER EVER say that I "believe" anything. — Frank Apisa

This is an aside, but I want to say that your demand for certainty, all or nothing, is unreasonable for this world. Sure, this horse experiment is not consequential, but a lot of things are. We are not certain that Climate Change is real, but being agnostic is not a choice in this case. Either we fight it or we don't. And a 97% agreement among experts (let's assume that part is true) is sufficient to pick a side.

Hume would simply say more people [...] are mistaken. — Wolfman

Why is this claim the most reasonable one? Appealing to the Principle of Parsimony, you (or Hume) have the onus of proof to defend it.

"I'm hallucinating" is a very simple explanation — Echarmion

No because it is abnormal (using common sense alone, the normal is to not hallucinate), and so we would need to further explain the cause of that abnormality. In contrast, we don't need to further explain the existence of an oasis, as it is not abnormal.

while I am hallucinating, perhaps I am also hallucinating the people that agree with me. — Echarmion

Might as well believe that the whole world is an illusion, on the mere grounds that it is logically possible. But logically possible does not entail reasonable. For this, we appeal to further principles of reasonableness like Parsimony.

The bigger issue is that you haven't justified the principle of parsimony. Why is the less complex explanation closer to reality? Is reality obligated to be simple and parsimonious? — Echarmion

This discussion defends the PUP on the grounds of Parsimony, which is indeed assumed. I am hesitant to defend that here, with fear that I would need to defend the premises for Parsimony etc. All I will say for now is that it is a perfectly accepted scientific principle, and that the alternative (that more complex is more reasonable) leads to a reductio ad absurdum: Can't prove there is no teapot in space? Then we'll believe there is.

The reason we can use the parsimony as a principle in the scientific method is because we're concerned with making predictions, which means making working models of reality. A simpler, more inclusive model is more useful than a complex, less inclusive one. But it's a tool for of practicality, not objectivity. — Echarmion

I'm not sure that statement makes sense. Reality implies objectivity. And as both philosophy and science aim to predict reality, what works for science for that aim also works for philosophy. Note also that the Principle of Parsimony was first introduced not for science but for philosophy; and that science is a branch of philosophy (ie the search for truth), specializing in what is empirically verifiable.

Hello.

Hume notes that the only things we can perceive are perceptions (i.e. internal and perishing existences), but the vulgar confuse perceptions with actual objects; that is, they confuse representations with what is actually represented. — Wolfman

Sounds good; I accept the correction on Hume's position. Then the PUP also solves that new problem; that the actual objects can reasonably be predicted if the perceptions are consistent among the subjects.

Yeah sure. That "problem" line was more of an intro to present the principle.

Anyway, I would like to be clearer about what exactly is the position you're attributing to Hume before considering whether what you are proposing is or is not an answer to it. — Nagase

It seems I have trouble clarifying to you what I think Hume is saying. But in a way it is not relevant, for the point of the OP is not to determine if I answer Hume's problem, but if the PUP is a valid principle.

This is admittedly nitpicky, but doesn't "knowing" imply certainty? Math is indeed certain. But for the horse story, there is the alternative possibility of collective hallucination (though of course nobody in their right mind would choose it I think).

That aside, whether we use the word belief or knowledge, it sounds like it is a yes. Now consider 2 scenarios with 10 subjects trying to determine if there is a horse in a field:
(1) 9 out of 10 subjects see a horse; the other 1 does not.
(2) 1 out of 10 subjects see a horse; the other 9 do not.

In which of the 2 scenarios is it more reasonable to believe the horse is real?

Hello.

You say a collective hallucination is "less likely" but what is that judgement based on? If you're basing it on empirical research on hallucinations, then you're just referencing another phenomenon, which might be just as illusory as any other. — Echarmion

I think I understand your point, that to quantify the likelihood or probability of hallucination demands a reference that must be more certain. But rather than using Probability, I am using Complexity of the explanation to appeal to the Principle of Parsimony. Regardless of the probability, the explanation that the object is real is simpler than the explanation of collective hallucination, because it would also need to explain where the hallucination comes from, and how come it is so consistent among all subjects etc.

Another example of using complexity instead of probability for reasonableness: If an object looks and sounds like a duck, it is more reasonable to conclude it is a duck than to conclude it is a robot piloted by an alien. This is not because we know the probability of that explanation, but its level complexity.

That is some Sixth Sense stuff right there! You may relax and know you are real because Cogito Ergo Sum. Even Bruce Willis was real; just not visible.

if one can hallucinate a unicorn, one can surely equally hallucinate a crowd of other people — unenlightened

True. Unless you have confirmed before that the crowd is real (through interacting with them in the past, or seeing, hearing and touching them, etc). Let's say that's the case here.

Also, if stuck on the unicorn idea due to it being inconceivable, then let's use a horse instead. Is it more reasonable to believe that the horse is real, or that it is an hallucination along with everyone else in the room and everything else you know in this world?

The idea that reality is to be decided by a vote is repugnant. — unenlightened

I agree only when it comes to votes based on opinions without reason. Otherwise, we do this all the time, and reasonably so. If 9 out 10 cancer experts claim you have cancer, is this not grounds to take the claim more seriously than if it was 1 out of 10?

No. He claims that you cannot draw conclusion about reality from perception.

Still missing the point. Let's tweet the story some more.
Replace unicorn with horse; replace room with "field on the other side of the fence" (so that you cannot verify its existence by touching it). You still wouldn't believe it is real?

I think he is in fact denying there is any connection between perception and reality. To him, making any claims about metaphysics is impossible.

Hello.
But some things CAN be perceived. And the PUP connects the perception to conclusions about reality, which is metaphysics.

Hello.

What they wonder is whether or not what they see is a mirage, which is a form of illusion, not a hallucination. — unenlightened

This is missing the point (which admittedly with hindsight is unsurprising when using the desert example). We could have used the perception of a unicorn in a room instead. If I am the only subject, then I would second-guess my perception, but if many subjects perceive the same unicorn, then it is reasonable to suppose that it is real, until given a reason to believe otherwise.

Furthermore, the case of a mirage does not work against the PUP. First, if there is a mirage of an oasis, then the oasis must still exist. Second, different subjects are not expected to perceive the mirage-oasis in the same fashion if they are seeing it from different locations. Third, is it not still more reasonable to believe the perceived oasis is real, if given no reason to believe it is caused by a mirage? Remember the PUP gives reasonableness, not certainty.

Hello.
Yes, this "intersubjective agreement" is very much what I am trying to describe in the PUP.

Hey there.
I am not sure if your post is intended to address my quote, but if it is, I must admit I don't understand anything you are saying. Sorry bro. Perhaps it could be a bit more concise?

Hello.

So how does the fact my mind does not appear to be my body provide evidence that my mind is eternal? — Bartricks

This is not in the OP, but here is my answer. It does not claim that the mind is eternal (for I believe it begins to exist), but that it survives the event of death.

- The human body can be defined as "all the physical parts of a person".
- Thus if the mind is not the body, then it it follows that it is non-physical.
- Since death is, as far as we know, only a physical event, then it does not affect non-physical things, and thus the mind must survive death.

So you claim that subjective topics, that is, matters of opinions, regard things for which we have little-to-no experience or knowledge, is that right?

I disagree with that. Sticking with the same apple example, even if we both take a bite out of the same apple, I can still make the honest claim "this apple tastes good", and you can make the honest claim "this apple tastes bad"; and this can simply be explained by the fact that I happen to like apples and you happen to dislike apples in general. Another classic example: we both look at the same piece of art, and you claim "this is beautiful" and I claim "this is ugly", and neither of us is wrong, because as the saying goes, beauty is in the eye of the beholder, that is, the subject.

Conversely, I can have zero knowledge and experience about angels, and yet making a claim such as "angels exist" is objective, because it is a matter of fact: they either exist or they don't.

Greatest degree: I know falling out of a tree certainly can hurt because I fell out of a tree once and it hurt like hell.
Lesser degree: I believe falling out of a tree hurts, but never having fallen out of a tree....I might get lucky, fall on a pile of leaves, and suffer no hurt.
No degree at all: experience and possible experience having been accounted for, there is no other degree of truth available, so there is no opinion on falling out of trees. Nevertheless, it is my opinion these statements are true. — Mww

Nevertheless, I mostly agree with these above statements on the degrees of knowledge. I would call the top one "certainty", the middle one "probability or reasonableness or methodical faith", and the last one "blind faith".