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?

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

Do you actually mean that there is no reason or do you just mean that the reasons given are inadequate?

Which ones — AmadeusD

Perhaps “one ought not harm another.”

what mind-independent feature — AmadeusD

Perhaps that one ought not harm another.

and how could that come to our sensibility if not through phenomenal interpretation — AmadeusD

Perhaps not all truths come to our sensibility through phenomenal interpretation.

For example, perhaps either it is a mind independent fact that the universe was created by a transcendent intelligent designer or it is a mind independent fact that the universe wasn’t created by a transcendent intelligent designer. Perhaps either it is true that it is sometimes reasonable to believe in something despite there being no phenomenal evidence or it is true that it is never reasonable to believe in something despite there being no phenomenal evidence.

Or must we be agnostic on all such things? But then what phenomenal evidence suggests that we must be agnostic on all such things?

Leontiskos brought up a good point: update 1 & 2 can now be condensed essentially into the following argument:

P1: If we do not know of any moral facts, then we have no reason to believe them.
P2: We do not know of any moral facts.
C: Therefore, we have no reason to believe them. — Bob Ross

Are you saying that we do not know that there are moral facts or are you saying that we do not know whether or not something like "you ought not harm another" is a moral fact? Because these are different things (e.g., I know that you have/had a mother but I do not know which woman is/was your mother).

I’m not trying to prove that one ought not harm another. I’m trying to make sense of moral realism. Moral realists claim that there is something like an objective, mind-independent fact that one ought not harm another, and that because of this fact the proposition “one ought not harm another” is true.

I’m not offering a syllogism. I’m using something like Tarski’s T schema.

“Electrons objectively, mind independently, are negatively charged particles” is true because electrons objectively, mind independently, are negatively charged particles.

“One objectively, mind independently, ought not murder” is true because one objectively, mind independently, ought not murder.

Demonstrating why something like that might be true could constitute merely pointing to a relevant fact about why it is wrong to harm people. — ToothyMaw

Asking why it’s wrong to harm people is like asking why electrons are negatively charged. There is no answer; some things are simply fundamental, brute facts. Explanations have to come to an end somewhere.

Sure, one might make mistakes in analyzing such explanations, but the moral person would search for those most true given a set of "brute facts". — ToothyMaw

One such brute fact might be “it is wrong to harm people.”

I know. Are you saying you are a realist and thus that your claim that one ought not murder is a moral fact? It sounds more like you are just adopting a pragmatic way of going about it that appeals to concepts like innocence and obligation and not actual fact hood. — ToothyMaw

I'm simply questioning the assertion that if one cannot derive an ought from an is then any claim of obligation is false.

Perhaps "you ought not harm another" is simply a brute fact about reality, much like "electrons are negatively charged particles" is.

If you cannot demonstrate why your particular morality is fundamentally more justified than another's, what reason do I have to follow it? — ToothyMaw

If by "what reason do I have to follow it" you mean something like "why should I believe you" then maybe you shouldn't believe me if I can't prove it.

But whether or not I can prove it and whether or not you should believe me is a separate issue to whether or not it is true.

If realism is correct then something can be both true and unprovable.

Why is it wrong to do that? — bert1

Why are electrons negatively charged?

I don't think there's a meaningful answer to the question. Some things are simply fundamental, brute facts about the world. Explanations have to come to an end somewhere.

Better questions are: "how do you know that it's wrong?" or "how can one verify that it's wrong?".

The proposition “there is a normative fact such that ‘one actually ought not harm another’” does not entail, if true, that “one actually ought not harm another” — Bob Ross

I'm not stating the former proposition; I'm stating the latter.

One actually, absolutely, really, categorically, objectively, super duper, ought not harm another.

I don't think I addressed Sirius...? — Banno

Yeah, sorry, got mixed up with another discussion. I meant Bob Ross.

My concern is simply that folk accept that there are moral truths. — Banno

That's fine, but there can be a big difference between the various ways that such truths are understood. Consider mathematics; both mathematical realists and mathematical ant-realists believe that there are mathematical truths, but there is a distinction between the Platonism of mathematical realism and the formalism of mathematical anti-realism. Or consider an example from the SEP article: there is a distinction between a diamond being made of carbon and a diamond being worth £1,000.

The question many want an answer to is if moral truths are comparable to Platonism/a diamond being made of carbon (realism), or to formalism/a diamond being worth £1,000 (anti-realism).

Yes, with respect what I regard as ‘moral’ signification, the word ‘morally’ is signifying in #1 that this is something you actually ought to be doing (and, in this case, more specifically, that you should not be harming others). — Bob Ross

I don't understand the distinction between something I ought to do and something I actually ought to do.

But fine, using your language:

A moral realist might claim that the statement "one actually ought not harm another" is made true by the mind-independent fact that one actually ought not harm another (much like someone might claim that the statement "electrons are negatively charged particles" is made true by the mind-independent fact that electrons are negatively charged particles).

... it will never be related as strongly as if it corresponded to a fact about reality (or something like that). — ToothyMaw

The realist will claim that that one ought not murder is a fact about reality, much like that an electron is a negatively charged particle is a fact about reality.

Why is the "ought" in "one ought not murder" morally compelling? — ToothyMaw

That's a different question. It might be true that one ought not murder even if knowing this doesn't compel me to obey. Perhaps I just don't care about what I ought or ought not do. Perhaps I enjoy doing things I shouldn't.

Meta ethics isn't concerned with what we actually choose to do.

I don't know what the philosophers are doing. — Inyenzi

Trying to make sense of and justify the many things we simply take for granted.

Let's keep it simple.

Electrons are negatively charged particles. How do I verify (or falsify) this?
One ought not murder. How do I verify (or falsify) this?

Assume that we can verify that electrons are negatively charged particles but cannot verify that one ought not murder. What then? Perhaps:

One ought not assert a claim that one cannot verify.

But then how do I verify (or falsify) this?

I have no problem, fundamentally, with this (other than labeling it as a moral realist position) because it didn’t specify the mind-independent fact of ‘one ought not harm another’ as morally signified. My argument doesn’t negate the possibility of normative facts—just moral facts. — Bob Ross

What would it mean for a fact to be moral? Do these two propositions mean different things?

1. one morally ought not harm another
2. one non-morally ought not harm another

If so then let's just rephrase my previous comment:

A moral realist might claim that the statement "one morally ought not harm another" is made true by the mind-independent fact that one morally ought not harm another (much like someone might claim that the statement "electrons are negatively charged particles" is made true by the mind-independent fact that electrons are negatively charged particles).

There are, broadly speaking, two types of derivation.

The first is to derive from a single premise:

a)
Premise: This is a red car
Conclusion: Therefore, this is a car

The second is to derive from more than one premise:

b)
Premise: If John is a man then John is mortal
Premise: John is a man
Conclusion: Therefore, John is mortal

So now let's consider obligations:

c)
Premise: One ought not murder
Conclusion: Therefore, one ought not murder John

d)
Premise: If John is innocent then one ought not kill him
Premise: John is innocent
Conclusion: Therefore, one ought not kill John

Perhaps you want an argument of these forms:

e)
Premise: Murder is Y
Conclusion: Therefore, one ought not murder

f)
Premise: If murder is Y then murder is Z
Premise: Murder is Y
Conclusion: Therefore, one ought not murder

I don't think either e) or f) can ever be valid. But so what? Why isn't c) or d) sufficient?

There seems to be this implicit claim that if "one ought not murder" cannot be derived from "murder is Y" premises alone then it cannot be true. What justifies this claim?

1. Naturalism is true

2. The linguistic and non-linguistic practices which do not refer to or supervene on any natural fact outside the linguistic and non-linguistic practices must solely depend on the collective mind judgements of the community. — Sirius

Moral realists reject 1 and/or 2.

To prove moral realism wrong you must prove 1 and 2 true. You haven't done so, only asserted them.

Although it would help if you could explain what you mean by naturalism. Do you mean physicalism? If so, what of mathematics?

I believe there is a fundamental disagreement between us regarding the ontological and logical status of possible states and actual states of affairs.

...

A true possible state of affairs is actual. — Sirius

Yes, there is a fundamental disagreement. My take is that truth is a "property" of expressions, i.e. speech, writing, thought, etc. As such, as you say, "true statements can only exist as cognitive content," given that speech, writing, and thought can only exist as cognitive content. But there's more to the world than speech, writing, and thought, and so that speech, writing, and thought can only exist as cognitive content isn't that the rest of the world can only exist as cognitive content.

But you seem to be arguing that truth is a property of other things (e.g. the states of affairs that speech, writing, and thought are about). It's not a position I agree with.

Even if I were to accept that truth is a property of these other things, note that these other things aren't statements. A true state of affairs isn't a true statement, and so that true statements can only exist as cognitive content isn't that true states of affairs can only exist as cognitive content. Your argument appears to equivocate.

Seems too strong to me.

A moral realist need only claim that "one ought not harm another" is either true or false.

A moral antirealist claims that it has no truth value...? — Banno

Your use of the term "moral realism" seems equivalent to what most philosophers mean by moral cognitivism, and your use of the term "moral antirealism" seems equivalent to what most philosophers mean by moral noncognitvism. Yours isn't the standard terminology.

See here:

Cognitivist theories hold that evaluative moral sentences express propositions (i.e., they are 'truth-apt' or 'truth bearers', capable of being true or false), as opposed to non-cognitivism.

...

Moral realism ... holds that such propositions are about robust or mind-independent facts, that is, not facts about any person or group's subjective opinion, but about objective features of the world.

...

Ethical subjectivism is one form of moral anti-realism. It holds that moral statements are made true or false by the attitudes and/or conventions of people, either those of each society, those of each individual, or those of some particular individual.

...

Error theory, another form of moral anti-realism, holds that although ethical claims do express propositions, all such propositions are false.

...

Non-cognitivist theories hold that ethical sentences are neither true nor false because they do not express genuine propositions.

Or if you don't like Wikipedia then see here:

Traditionally, to hold a realist position with respect to X is to hold that X exists objectively. On this view, moral anti-realism is the denial of the thesis that moral properties—or facts, objects, relations, events, etc. (whatever categories one is willing to countenance)—exist objectively. This could involve either (1) the denial that moral properties exist at all, or (2) the acceptance that they do exist but this existence is (in the relevant sense) non-objective. There are broadly two ways of endorsing (1): moral noncognitivism and moral error theory. Proponents of (2) may be variously thought of as moral non-objectivists, or idealists, or constructivists. So understood, moral anti-realism is the disjunction of three theses:

1. moral noncognitivism
2. moral error theory
3. moral non-objectivism

Sirius is arguing against moral realism as described above, not against moral cognitivism in general.

If my OP is true, then this position would be false because moral statements are not made true by some mind-independent feature of the world (i.e., they are not moral facts). — Bob Ross

A moral realist might claim that the statement "one ought not harm another" is made true by the mind-independent fact that one ought not harm another (much like someone might claim that the statement "electrons are negatively charged particles" is made true by the mind-independent fact that electrons are negatively charged particles).

I don't see how you've shown that this can't be the case.

Also, there are infinitely many numbers, right? — RogueAI

Not in the Platonic sense. Numbers don't exist. Rather, when we say that there are infinitely many numbers we are just saying that we can (in principle) keep adding 1 forever.

You take facts to be possible states of affairs, which must either be true or false. — Sirius

Statements are true, states of affairs obtain. A statement is true if it describes a state of affairs that obtains, and false if it describes a state of affairs that doesn't obtain.

There are a finite number of statements but (possibly) an infinite number of states of affairs. Statements depend on "cognitive content" but (some) states of affairs don't.

3. There are infinitely many statements that are necessarily true, independent of spacetime itself — Sirius

I dispute this. There may be infinitely many facts, but it does not follow that there are infinitely many true statements. Some facts just aren’t talked about.

At the very least you can say that there are infinitely many possible true statements, but I don’t think that requires an all-encompassing mind.

Let’s take a simple example: one ought not harm another.

Broadly speaking there are three different approaches.

1. The moral nihilist will argue that no statements of this kind are true.

2. The moral anti-realist will argue that some statements of this kind are true and are made true by some mind-dependent feature of the world.

3. The moral realist will argue that some statements of this kind are true and are made true by some mind-independent feature of the world.

I don’t quite see how your argument proves 2 and/or disproves 1 and 3.