How do you know this? — baker

I actually rephrased my claim to say "there is an objective, mind-independent, non-physical fact-of-the-matter."

It is by definition impossible to detect the difference between reality and a perfect simulation of reality.
If the simulation is less than perfect then there may be tell-tale signs.
If (for example) reality is a projection from one's own mind, then one might see signs of this. — PL Olcott

Sure. But if one had only ever experienced a poor simulation of reality and never experienced reality then one wouldn't know that one was experiencing a poor simulation of reality and not experiencing reality.

Perhaps in reality grass is red and the Earth has two moons.

And they would be wrong in every sense of the word, unless invoking a supernatural source of morality. — AmadeusD

What do you mean by "supernatural"? Do you mean "non-physical"? Well, yes. Moral realists don't usually claim that moral facts are physical facts. Just as mathematical realists don't usually claim that mathematical facts are physical facts.

It's my gut feeling against theirs. — baker

Precisely. You have a gut feeling that moral realism is false. They have a gut feeling that moral realism is true. One of you is right and one of you is wrong. Neither has empirical or self-evident rational justification.

But there is an objective, mind-independent, non-physical fact-of-the-matter (either moral realism is correct or it isn't). So at the very least moral realism isn't inherently incoherent in arguing that there are objective, mind-independent, moral facts-of-the-matter.

I believe the topic is physical things in the real world. — Patterner

How do I know that I am perceiving a physical thing in a real world and not just dreaming or hallucinating or being tricked by an evil scientist who has my brain in a vat and is stimulating my visual cortex with nanomachines?

This question seems relevant to the discussion.

Yes. Because guts aren't reasonable. — baker

How do you know this?

Of course things we aren’t perceiving exist. — Patterner

I don't perceive Santa. Does he exist?

How could I perceive something that doesn’t exist? — Patterner

Dreams? Hallucinations? A VR headset?

To me, a state of affairs is an actual, obtaining situation in the world independent of further judgement. — AmadeusD

And the moral realist will claim that that one ought not harm another is an actual, obtaining situation in the world independent of further judgement.

But it patently is not a state of affairs — AmadeusD

How so? What does “state of affairs” mean to you?

What state of affairs outside of the mind indicates that command is universal? — AmadeusD

That one ought not harm another is the mind-independent state of affairs.

How does a moral realist know something is false? Because their "gut feeling" tells them so? — baker

Possibly.

Do you claim that it is unreasonable to claim to know that something is false because their “gut feeling” tells them so? If you do, how do you know this? Is that your “gut feeling”?

I have no problem with that formulation, i would just prefer to not use the term 'objective' as neither my example, or stretching to obligation, actually speaks to a state of affairs. — AmadeusD

Realists will disagree. That I ought not harm another is as much a state of affairs as that 1+1=2 and that electrons are negatively charged particles and that it will rain over my house tomorrow.

How do moral realists resolve descriptive moral relativism?
How do moral realists explain that different people have different ideas about what is right or wrong?
How do moral realists explain that some people believe that murder is wrong, but some other people believe that murder is not wrong? — baker

I don’t understand the relevance of your questions. People can believe different things about maths and physics and so on, but there are nonetheless right and wrong answers. So too with ethics.

It is one state of affairs among many. Now what? — baker

I’m not sure what you mean. Yes, there are many states of affairs: one ought not murder, my name is Michael, it will rain over my house tomorrow, etc.

You can, it's just not persuasive to the person who believes we ought to harm another, so our differences remain even as you call it a state of affairs. — Moliere

Whether or not it’s persuasive is a separate matter. Flat Earthers often aren’t persuaded.

I’m only trying to explain moral realism, not argue that it’s correct. Moral realists might claim that a moral statement like “you ought not murder” is true because that you ought not murder is a brute, mind-independent state of affairs.

As for how to justify such a claim, they might accept that there is no empirical evidence, but argue that not all justifications are empirical. Certain rational truths simply have no empirical evidence.

But it is objective, in the sense that, it is - given that artificial definition - inarguably and necessarily in that category. — AmadeusD

The same might also be true of obligation. Given the artificial definition of the words “you”, “ought”, “not”, “harm”, and “another” it is necessarily the case that you ought not harm another.

What we say is made true or false because of the states of affairs of the world. — Moliere

And why can’t it be that one such state of affairs is that we ought not harm another?

I'm wanting to know what is at the bedrock of that claim, to support it, in objective terms? — AmadeusD

There seems to be this assumption that it can be an objective brute fact that gravity exists, that pi is irrational, and that I would never have been born had one of my parents died in their childhood, but that it cannot be an objective brute fact that one ought not harm another. Why is that?

a world that I have defined as a non-perceptual exteriority beyond subjectivity that also encompasses subjectivity. — JuanZu

I have no idea what this means.

My use of the term is what I believe is most common.

But rather than split hairs over the meaning of “external world” I’ll be more specific with my claim:

Some objective truths (such as those of mathematics) do not depend on the mind-independent existence of matter, energy, space, time, or abstract objects.

I claim that the essence of objective truths cannot be reduced to either perception or subjectivity — JuanZu

You’re doing more than that: you’re claiming that objective truths depend on the existence of an external world, but this is false.

If only my mind exists then it is objectively true that nothing other than my mind exists (even I were to believe otherwise), and this objective truth cannot be reduced to either perception or subjectivity.

Do mathematical truths have nothing to do with matter and energy? I agree, that's why I'm not a physicalist. — JuanZu

Physicalism is a position regarding what sorts of things exist.

Your claim here suggests that you think that a statement can only be true if it "corresponds" to something that exists, and so that if a true statement is about something non-physical then it must correspond to some non-physical thing that exists.

This is a mistaken view. Not all truths depend on the existence of something.

If you are not a Platonist, mathematical objects may depend on or be nothing more than objects emerging from brain processes. And a physicalist will have to demonstrate that. The conclusion you reach is false. But my argument holds. If we are not Platonists we can say that truths depend on a world beyond the perception that guarantees their possibility. We can, if we are not Platonists, say that we are only talking about physical and chemical processes that occur in the brain and that a mathematical truth is based on these processes. — JuanZu

Mathematical (and other formal) truths have nothing to do with matter, energy, space, time, or Platonic entities. Yours is a false dichotomy.

"All As are Bs, all Bs are Cs, therefore all As are Cs" is a valid argument.

The above statement is objectively true and does not depend on the existence of an external world. Its truth has nothing to do with matter, energy, space, time, my brain, your brain, or a hidden realm of immaterial, magical entities that is somehow able to attach itself to our thought processes.

That the world exists (an abstract concept) is verified to be true (also an abstract concept) on the basis of anything that appears to be any physical sensation (not merely an abstract concept). — PL Olcott

But what isn't verified is that there is more to the world than those physical sensations.

The pain is conclusive proof that the fist exists. — PL Olcott

Pain can be caused by things other than fists.

The argument holds regardless of whether you are a Platonist or not. — JuanZu

If Platonism isn't true and there is an external world then the external world is exhausted by matter, energy, space, and time.

If mathematical truths depend on the existence of an external world and if Platonism isn't true then mathematical truths depend on the existence of matter, energy, space, or time.

Mathematical truths do not depend on the existence of matter, energy, space, or time.

Therefore, either Platonism is true or mathematical truths do not depend on the existence of an external world.

I am not talking exclusively about material objects. You can, if you want, consider numbers, logic, ideas, theories, etc., as Non-material objects or ideals [or as a kind of materiality that is not reducible to physicalism]. But the important thing is that its existence along with mine cannot be reduced to perception. — JuanZu

I'm not a Platonist. I don't believe that non-material objects or ideals "exist". As such I'm not a mathematical realist; I'm a mathematical antirealist. But even mathematical antirealists can believe in the objective truth of mathematics (in the sense that we might all be wrong).

Something is true even if I am no longer alive to perceive it, be it the truths of physics, mathematics, etc. — JuanZu

That doesn't mean it depends on an external world.

Mathematical truths, for example, do not depend on the mind-independent existence of matter, energy, space, or time.

Or maybe you mean something else by "external world"? You haven't been clear.

Maybe a better approach would be to address the relevant differences between these:

1. The baby exists
2. The baby is crying
3. The baby was born in October
4. The baby will be going to see the doctor tomorrow
5. The baby wouldn't have been born had her parents never met
6. You ought not eat the baby
7. 1 + 1 = 2

Which are truths? Which are facts? Is there a relevant difference between being a truth and being a fact? Does it matter if something is a fact but not a truth or a truth but not a fact?

Surely all that matters is whether or not the baby is crying, whether or not you ought not eat the baby, whether or not 1 + 1 = 2, etc.? Forget the terms "truth" and "fact" if they're causing you so much trouble.

More just noting that this is not how we normally use the word "fact", at least -- usually we mean word-to-world, where the words are meant to set out how the world is. — Moliere

Why can't "you ought not harm another" set out how the world is? I guess I'm just not really sure what you mean by "how the world is"?

where truths might include more than features of the world or how it is and so can include statements like "One ought such and such" — Moliere

Why can't this be a feature of the world?

... there are no better reasons to affirm your existence than the existence of the world. — JuanZu

Arguing that the existence of an external world is the best explanation for my existence is different to arguing that objective truths depend on the existence of an external world. I'm arguing against the latter, not the former. I can (and do) accept the former.

What I claim is that any statement you make about your existence presupposes conditions of truth and objectivity. — JuanZu

Which doesn't require an external world. If only my mind exists then it is objectively true that a mind-independent material world doesn't exist (and even if I believe otherwise).

then your existence is a "property" that can only be validated by going beyond the perception. — JuanZu

My perceptions depend on my existence, therefore awareness of my perceptions validates my existence -- and I am aware of my perceptions.

How exactly would I "go beyond" my perceptions anyway? It's really not clear to me now if you're arguing for external world realism or nihilism.

If you assume that only your mind exists, you can no longer ask about the existence of the external world, you have already closed the way to answering that question. — JuanZu

I'm showing that there can be an objective truth about what does and doesn't exist even if there isn't an external world, and so your claim that an external world is required for there to be an objective truth about what does or doesn't exist is false.

If only my mind exists and if I believe that a mind-independent material world exists then my belief is objectively false and it is objectively true that a mind-independent material world doesn't exist.

it requires, so to speak, an impersonal and non-subjective space of validation — JuanZu

What's a "space of validation"? It certainly seems very different to what most mean by "external world". Most mean something like a collection of material objects extended in space, behaving according to some set of physical laws, with our perceptions being a byproduct of these processes. It's certainly not a truism that this is required for "this perception exists" to be true.

You are not taking into account the conditions of truth and objectivity. For the statement "This perception exists" to be true, it requires, so to speak, an impersonal and non-subjective space of validation. Which would have been demonstrated in the example of the future statement. Therefore, ontologically, perception is one more thing among other things in the impersonal and non-subjective world. That is to say, we cannot doubt the existence of the "external world" more than our own perception. — JuanZu

I think you're being ambiguous with your use of the term "external world", and this is open to equivocation. Consider again my example above:

1. Only my mind exists
2. I believe in the existence of a mind-independent material world

My belief in the existence of a mind-independent material world is objectively false, but only my mind exists.

Is there an external world in this situation?

What I have stated is precisely that existence can no longer be reduced to perception. — JuanZu

You seem to be arguing that both (1) and (2) are true:

1. "things external to my perception exist" is true only if things external to my perception exist
2. "I exist" is true only if things external to my perception exist

(1) might be true (even a truism) but (2) is a non sequitur, and the claim that (2) is true because (1) is true is also a non sequitur.

All we can say a priori is that:

3. "I exist" is true only if I exist

In this sense, if "existing" says something about me then it can only be true on the condition that my existence is also something non-perceptual. — JuanZu

If your existence just is the occurrence of your perceptions then your existence isn't non-perceptual.

And on the contrary, the conditions of truth and objectivity seem to presuppose a world beyond my perception. — JuanZu

Assume for the sake of argument that only your mind exists (i.e. metaphysical solipsism is correct).
Assume also that you believe in the existence of a mind-independent material world.

It is both the case that there isn't a world beyond your perception and the case that there is an objective truth (and which incidentally is contrary to your beliefs).

Mind-independent truths do not depend on the existence of mind-independent things.

My belief on the existence and working of the brain, which I have never seen is based on the information I have read from the books and Biology classes in the school.
This is a belief in different type, nature and form on its foundation. — Corvus

I'd hazard a guess that you believe in the existence of a brain that you cannot see because its existence is part of a parsimonious theory with explanatory and predictive power, and that you believe it is reasonable to believe in a parsimonious theory with explanatory and predictive power?

Well, the same is true for the cup; the (continued) existence of a cup that I cannot see is part of a parsimonious theory with explanatory and predictive power, and so it is reasonable to believe in the (continued) existence of a cup that I cannot see.

Furthermore, presumably you believe that your brain behaves (more or less) according to the physical laws as described by our best scientific theories? Well, such theories also include laws against creation (and destruction) from nothing, and that things don't simply change apropos of nothing acting upon them (whether internally or externally). The claim that cups just come into and out of existence depending on the direction we face (or depending on whether or not our eyes are open) is contrary to many of the physical laws as described by our best scientific theories.

It seems like special pleading to believe in the existence of your brain but not in the existence of a cup that you cannot see. It is reasonable to believe in either the existence of both or the non-existence of both. So I think you need to either accept materialism or commit fully to idealism.

Yes, I do accept the brain is the biological organ where all the mental events happens. But at the same time, brain is the blackbox i.e. we don't know how it is connected to our perceiving the cup. — Corvus

So you believe in the existence of your brain even though you don't ever see it? Then you clearly have reasons for believing in the (continued) existence of something that you cannot see. Why is it a stretch to extend this reasoning to other things, like the wider central nervous system, your eyes, the light that stimulates your eyes, and the cup that reflects the light?

At what point does it suddenly become unreasonable to believe in the existence of something that cannot be seen, and why there?

I'm asking about the brain; do you accept that we have a brain and that brain activity is causally responsible for us seeing a cup (when we do in fact see a cup)?

We need to work backwards from the common denominator (seeing a cup) to find out where our disagreement starts.

Then let's start with something that I'm sure most will agree with and work backwards; when we see a cup we see a cup.

The next step backwards many will accept is that seeing a cup is reducible to or an emergent phenomena of brain activity.

Do you disagree with the claim that we have a brain and that brain activity is causally responsible for us seeing a cup?