Your argument shows that we cannot know if realism is true or not. But that does not entail that realism is not true. That just leaves us stuck having to either assume one way or the other, because our actions will tacitly entail such an assumption (e.g. if we try to figure out what is real or not, to discern truth from falsehood, we are tacitly assuming that there is something real; if we go about acting like truth and falsehood don't matter and just believe whatever because no reason, we are tacitly assuming nothing is real).

It then becomes a practical question of which assumption is more useful, and I argue that if we cannot know whether or not anything is real, it is more useful to assume that something is real and then try to figure out what it is, than to assume the opposite; because if we assume the opposite then we will inhibit any possibility of ever figuring out what is real, if it should turn out that anything is; and although there might turn out not to be anything real even if we do assume there is, and so we might make no progress at figuring out what it is, we at least have a chance to do so if we try that, and in doing so, tacitly assume that there is something real to be figured out.

An issue here is focusing on individual things. So if I'm no longer observing the sun, then I can't know whether the sun still exists according to the argument. But a lot of things stand in relation to the sun existing, such as the temperature of the planet on which I live, plants continuing to photosynthesize, and so on.

An even better example is that the ground continues to hold me up even when I'm not aware of it. I can continue to breathe air, and my heat continues to pump blood, and I only become aware of those things if something causes me to breathe irregularly, such as when encountering smoke, or exerting myself.

The best example is having a body. I'm not aware of most of it most of the time. Yet I keep on having experiences with eyes, ears, legs, arms, a back, etc. So the realist argument can be one of focusing on how all the things connect together such that they cannot cease to be what they are when we don't know, since our experiences continue on as if they were still what we know them to be.

On a cosmological level, take inertia. Inertia is the result of all the mass in the universe resisting your acceleration. So if the rest of the universe didn't exist when the car suddenly stops, then there's no reason for you to lurch forward. Similarly, before the germ theory of disease, there's no reason for people to get sick from viruses and bacteria if those didn't exist.

Ever noticed how much these arguments resemble the scholastic discussions of the existence of god?

I have noticed that my general counterargument to regressive or otherwise cynical arguments for nihilism of any sort does resemble Pascal's Wager, if that's what you're thinking of.

The notable difference between my argument and Pascal's is that Pascal concludes that therefore you should believe in some specific thing (the Christian God), when the same argument could be used equally well to argue that you should believe in different contrary things (e.g. other gods), whereas my argument only concludes that you should believe something or another is real, without any specificity as to what that is: just run with the assumption that there is some objective reality and then try to sort out the specifics about it, and maybe fail entirely if there actually is none, but also stand a chance of maybe succeeding at that, if such a thing as success at that is possible. I also apply the same argument to investigations of objective morality. And more generally to all practical endeavors in life: assume success is somehow or another possible and then try to figure out how; you might still fail anyway, but if you assume failure is a foregone conclusion and don't even try, you only guarantee it.

I'm going to translate your argument in terms of something concrete. Consider an apple on Bob's kitchen table, which I'll abbreviate as 'the apple'.

P1) The realist argues that “the being of the apple is independent of its being known.”
P2) In order to know whether or not "the being of the apple is independent of its being known," one must “know the apple when the apple is not being known.”
P3) In order to compare “the being of the apple as known” to “the being of the apple when it is not being known,” one must “know the apple” and “know the apple when it is not being known.”
P4) One cannot “know the apple when it is not being known” without performing a contradiction.
C) Therefore, the realist position is untenable.

P1 states a definition, i.e., what realism means, or how a realist uses their words. P2 says that to know whether or not that definition is true would entail knowing that the apple exists at those times that it is not known to exist - a contradiction.

So one counterargument is that a definition operates like an axiom in mathematics. An axiom is not something that is itself proven via a rule or process. Instead you either use it or not for pragmatic reasons.

Right, and that axiom must be taken as a “given.” However, I wouldn’t say that giving the realist position the status of axiom renders it “off limits” to the skeptic who is unconvinced of its supposed “self-evidence.”

P2) In order to know whether or not "the being of X is independent of its being known," one must “know X when X is not being known.” — PessimisticIdealism

This seems contentious. It seems to me that the realist claim would turn upon the limits of knowledge as such, and not knowledge about some thing or another (even when construed negatively). That is, I don't need to 'know X when X is not being known'; I simply need to know that knowledge is always finite in some manner.

It's like saying: 'in order to know that I can't see the back of this screen, I must know that I'm not looking at the back of this screen. But I can only know that if I know what it looks like. Therefore, I must be able to see the back of this screen in order to say that I can't see it'. Which is plainly ridiculous of course. The reason, of course, is that I understand not something about the object ('what it looks like'), but something about the nature of sight - it is perspectival. Mutatis mutandis, the same goes for your argument: I don't need to know X when X is not being known, I simply need to 'know' the limits of knowledge itself. Or to put it one last way: it's not 'knowledge about X' that's necessary, it's 'knowledge about (the limits of) knowledge)'.

P1) The realist argues that “the being of X is independent of its being known.” — PessimisticIdealism

This realist doesn't.

It's always easiest to argue against another when one misunderstands to begin with.

This realist doesn't. — creativesoul

Wouldn't a realist have to make that argument? A galaxy millions of light years away or an evolutionary ancestor would exist as they are regardless of whether we ever know, if galaxies and ancestor organisms are real.

Otherwise, "realism" dissolves into man is the measure, which would some form of Kantianism or anti-realiism.

The entire point about something being real is that it exists independent of us, whether we know it or not.

Wouldn't a realist have to make that argument? A galaxy millions of light years away or an evolutionary ancestor would exist as they are regardless of whether we ever know, if galaxies and ancestor organisms are real.

Otherwise, "realism" dissolves into man is the measure, which would some form of Kantianism or anti-realiism. — Marchesk

Mt. Everest existed in it's entirety prior to it's discovery.

A galaxy millions of light years away would exist regardless of whether or not we know about if there were such a thing that we didn't know about.

What argument needs made here?

What argument needs made here? — creativesoul

That realism requires things existing regardless of whether we know about them, which I understood OP's starting point to be.

Are you suggesting that an argument needs to be made for the following statement...

"Mt Everest existed in it's entirety prior to it's discovery?

Mt Everest existed in it's entirety prior to it's discovery? — creativesoul

We certainly have had such arguments on the old forum regarding Everest, apples and chairs. They tended to go over a 100 pages.

But yes, for everyday object realists, the mountain existed prior to humanity.

We certainly have had such arguments on the old forum regarding Everest, apples and chairs. They tended to go over a 100 pages.

But yes, for everyday object realists, the mountain existed prior to humanity. — Marchesk

Yup. It seems necessary to have them once again...

I'm a bit puzzled by the second part. If it is the case that Mt. Everest existed in it's entirety prior to it's discovery, then it does not matter what one's philosophical bent may be... Mt. Everest existed in it's entirety regardless of whether or not one believes that.

If it is the case that Mt. Everest existed in it's entirety prior to it's discovery, then it does not matter what one's philosophical bent may be... Mt. Everest existed in it's entirety regardless of whether or not one believes that. — creativesoul

Agreed, but three possible objections:

1. How do we know that to be the case?

2. What if the concept of things existing independent of us (or perception) was incoherent?

3. What if mountains and everyday objects is just a human (or animal) carving up of the world?

All of these arguments have been made against mountain realism. I'm not saying they necessarily succeed, only that it can be a contentious topic in philosophy.

If it is the case that Mt. Everest existed in it's entirety prior to it's discovery, then it does not matter what one's philosophical bent may be... Mt. Everest existed in it's entirety regardless of whether or not one believes that.
— creativesoul

Agreed, but three possible objections:

1. How do we know that to be the case?

2. What if the concept of things existing independent of us (or perception) was incoherent?

3. What if mountains and everyday objects is just a human (or animal) carving up of the world?

All of these arguments have been made against mountain realism. I'm not saying they necessarily exceed, only that it's a contentious topic in philosophy. — Marchesk

Regarding 1.

Please set out the referent of "that".

Regarding 2.

Discard such a concept.

Regarding 3.

Carving needs something to be carved.

Please set out the referent of "that". — creativesoul

How do we know "that" numbers exist? Morality, qualia, possible worlds?

Just because you can put a that in front doesn't mean it has a real referent, and we all will take issue with some class of things being considered real.

Whoa...

You asked, "How do we know that to be the case?"

Please set out the referent for the term "that". I'm trying to answer the question. I want to know that I understand what you're talking about. We've not been discussing any of those things you just mentioned. We could later, if it goes there... and it ought!

Please set out the referent for the term "that". I — creativesoul

Oh okay, Cart, horse, idealists being trampled.

Mount Everest is the reference of "that". How do we know that Mt. Everest existed before we knew about it?

I have to say I mostly agree with this argument. Consider what follows as footnotes.

P1) The realist argues that “the being of X is independent of its being known.” — PessimisticIdealism

This seems to me a description of modern or scientific realism, which, arguably, is not a philosophical position at all, but a methodological constraint. In other words, this kind of realism seeks to understand the object of its analysis whilst bracketing out, as far as is possible, subjective factors which is sees as extraneous to the object of analysis. It is typical of post-Copernican science, and indeed is example of the so-called 'Copernican principle', which 'states that humans, on the Earth or in the Solar System, are not privileged observers of the universe.' However what this attitude occludes, is just what the argument throws into relief, namely, that even objective knowledge has a subjective pole or aspect, in that it is a cognitive act by a scientist or number of scientists. I think the reason this is most often overlooked, is because the subjective pole of knowledge is relegated by post-Copernican science to the domain of 'secondary qualities', i.e. derivative of the purported primary qualities.

How do we know that Mt. Everest existed before we knew about it? — Marchesk

'Before' implies duration, duration is predicated on there being time, and time is somehow dependent on the perspective of an observer.

If Mt Everest were endowed with sentience, he/she/it would probably be incapable of cognising h. sapiens, because we're so tiny, and our lives so ephemeral, that they wouldn't even register in his/her/its
consciousness. Glaciers and rivers, maybe, because they stick around long enough to (ahem) make an impression.

'Before' implies duration, duration is predicated on there being time, and time is somehow dependent on the perspective of an observer. — Wayfarer

And yet we know about deep time, and we can measure how long Everest has been around.

If Mt Everest were endowed with sentience, he/she/it would probably be incapable of cognising h. sapiens, because we're so tiny, and our lives so ephemeral, that they wouldn't even register in his/her/its
consciousness. Glaciers and rivers, maybe, because they stick around long enough to (ahem) make an impression. — Wayfarer

Probably, but we also know about picoseconds and nanometers, so it's not impossible for a society of sentient mountains to learn about life.

Please set out the referent for the term "that". I
— creativesoul

Oh okay, Cart, horse, idealists being trampled.

Mount Everest is the reference of "that". How do we know that Mt. Everest existed before we knew about it? — Marchesk

That doesn't work. Here's the question again...

"How do we know that to be the case?"

Substitution leaves us with "How do we know Mt. Everest to be the case?"

That question doesn't make sense to me. Does it to you? Is that what you meant to ask?

...time is somehow dependent on the perspective of an observer... — Wayfarer

No. No. No. No.

And yet we know about deep time, and we can measure how long Everest has been around. — Marchesk

Of course. This is where, as I've often noted, Kant's notion of the compatibility of empirical realism and transcendental idealism. In other words, Kant did not deny the empirical reality of time and space (indeed Kant's 'nebular hypothesis' is still part of current science.) But he still maintained that in some fundamental sense, time itself was a 'primary intuition' of the observing intelligence, and denied that it had absolute or objective reality; that science itself is still dealing with the realm of phenomena.

...time is somehow dependent on the perspective of an observer...
— Wayfarer

No. No. No. No. — creativesoul

You panic because your sense of the nature of reality is being called into question. Do not adjust your set, this is a philosophy forum and it's normal programming.

That question doesn't make sense to me. Does it to you? Is that what you meant to ask? — creativesoul

No, but I can substitute real in there: How dow we know Mt. Everest is real?

Cue ordinary language response.

But he still maintained that in some fundamental sense, time itself was a 'primary intuition' of the observing intelligence, and denied that it had absolute or objective reality; that science itself is still dealing with the realm of phenomena. — Wayfarer

Right, does Kant ever say positively what exists and how it relates to the phenomena? So if time is a mental category, then what does it relate to in the real world?

Right, does Kant ever say positively what exists and how it relates to the phenomena? So if time is a mental category, then what does it relate to in the real world? — Marchesk

You notice the hidden assumption in your last question? The 'real world'? We need to see that we have a role in 'creating' that 'real world' - that's what your brain, the most complex known natural phenomena, devotes its energies to doing. And consumes a large amount of oxygen and nutrients to keep it going. Anyway I'm bowing out, I don't want to hijack the thread.

Anyway I'm bowing out, I don't want to hijack the thread. — Wayfarer

Wait, what? This is going to be the new 100 page idealism/realism death match. It's way too early to bow out.

You notice the hidden assumption in your last question? The 'real world'? — Wayfarer

So are you saying Kant didn't think the noumena was real?

...time is somehow dependent on the perspective of an observer...
— Wayfarer

No. No. No. No.
— creativesoul

You panic because your sense of the nature of reality is being called into question. Do not adjust your set, this is a philosophy forum and it's normal programming. — Wayfarer

Some implies more than one. Somehow implies more than one way for time to be dependent upon an observer.

"No. No. No." applies to one kind of dependency. Care to readjust your set or are you in the mood to talk about something that's not on mine?

Time cannot be existentially dependent upon the perspective of an observer because all perspective is accrued and as such requires time in order to develop.

Check.

Mate.

That question doesn't make sense to me. Does it to you? Is that what you meant to ask?
— creativesoul

No, but I can substitute real in there: How dow we know Mt. Everest to be real? — Marchesk

That's a different question entirely.

Oh okay, Cart, horse, idealists being trampled. — Marchesk

A reductio ad absurdum is not about the person guilty of holding belief that leads to such. Rather, it's about offering strong ground for rejecting such belief(good reason to abandon it).

If it is the case that Mt. Everest existed in it's entirety prior to it's discovery, then it does not matter what one's philosophical bent may be... Mt. Everest existed in it's entirety regardless of whether or not one believes that.
— creativesoul

Agreed, but three possible objections:

1. How do we know that to be the case? — Marchesk

Please fill in the value of the term "that". To what are you referring?