External to my body is locational in that the pen is in a different location to my body.

External to my mind seems to be non-locational. My position is that the pen is in my mind and that I cannot know whether it has an existence independent of my mind. — philosophy

So then you're equivocating the term "external" (you're using the same term to mean different things from one sentence to the next)

..Now since nothing is ever present to the mind but perceptions...it follows that 'tis impossible for us so much as to conceive or form an idea of any thing specifically different from ideas and impressions. — philosophy

Was Hume channeling a future Berkeley here? Radical empiricism does logically end up at idealism, so it's not terribly surprising. I just wasn't aware that Hume actually made an argument for idealism.

If I'm not mistaken, Hume was writing after Berkeley.

Although I think it is fair to call both Hume and Berkeley ''idealists'', they are idealists in different senses.

Berkeley is an ontological idealist in that he believes that only ideas exist.

Hume is an epistemological idealist in that he believes that all that he can know to exist are ideas.

I agree regarding radical empiricism logically leading to idealism. Kant attempted to solve this problem by conceding to the empiricists that all knowledge begins with experience, but adding that it does not follow from this that all knowledge arises out of experience.

Anyway, you don't need to explain what idealism is in this thread. We should get back to the fact that it's no more irrefutable than realism is.

But it still seems to me that realism is refutable in a way that idealism is not.

Realism is refutable in that it commits one to a contradictory term, ''unperceived object''. To quote Hume on unperceived objects:

''We may observe, that 'tis universally allow'd by philosophers, and is besides pretty obvious of itself, that nothing is ever really present with the mind but its perceptions or impressions and ideas, and that external objects become known to us only by those perceptions which they occasion...Now since nothing is ever present to the mind but perceptions...it follows that 'tis impossible for us so much as to conceive or form an idea of any thing specifically different from ideas and impressions.''

"Unperceived object" isn't a contradictory term. "Object" doesn't mean "perceived."

And just because Hume says something, that doesn't mean it's correct.

I haven't said that just because Hume says something it must be correct; I quoted him to better clarify my position.

How do you know that an object can exist independently of perception? You can never know this since it is, by definition, that which is independent of perception, i.e. experience. The realist, in positing a mind-independent world, is making a claim beyond experience.

Re Hume, for one, re this: "external objects become known to us only by those perceptions" I'd agree in the sense that we'd be talking about how we initially learn about things, stressing that it's also important that we do not conflate perception as a mental event with what we're perceiving or what the perception is of or even the content of the perception.

"Unperceived object" isn't a contradictory term. "Object" doesn't mean "perceived." — Terrapin Station

I don't agree with it, but the argument is that unperceived objects can't be known, not that they can't exist. Well, Berkeley tried to argue that unperceived objects were incoherent, but Hume is just saying that only what's perceived can be known.

EDIT: Actually, I take that back. The Hume quote is arguing that they are inconceivable. That's kind of shocking.

How do you know that an object can exist independently of perception? You can never know this since it is, by definition, that which is independent of perception, i.e. experience — philosophy

That would follow if you're using "know" to refer to "things that I'm perceiving." Why would you use the term "know" that way?

Because I know that I am perceiving what I am perceiving. I cannot know whether what I am perceiving exists independent of my perception of it since this would entail my perceiving an unperceived object, a contradiction in terms, hence refuted.

Again, I believe that the realist position leads to a contradiction in terms that the idealist position does not lead to. Hence, one is refuted whilst the other is not.

The realist, in positing a mind-independent world, is making a claim beyond experience. — philosophy

Yes they are, but that's because it makes sense. Otherwise, how could you be born or die? How do we account for all these experiences of an external world with things we can't see that effect us?

The idealism that you're arguing for makes all experience brute and mysterious, and it turns the known universe into perception. That means anything external to my experience is only known as an idea. That's a very small world.

Did you honestly just say that you're using the term "know" to refer to "things that I'm perceiving" because you know that you're perceiving what you're perceiving?

I completely agree that it makes sense. Hume would as well (can't remember the exact passage but he says ultimately that once he's stopped philosophizing he's going to live like any other person and accept the existence of external objects).

The point, however, is that said existence cannot be justified on the basis of reason but on faith. I believe that a world independent of my mind exists but I cannot possibly know this.

So I agree with your point, but it does not constitute a refutation of (epistemological) idealism.

I distinguished between knowledge of what I am perceiving and knowledge of that which is beyond my perception. The idealist affirms that you can know the former but not the latter. The realist maintains that you can know both. I have shown that the realist's position leads to a contradiction in terms. Hence, the position of the realist is refutable in a way that that of the idealist is not.

The point, however, is that said existence cannot be justified on the basis of reason but on faith. I believe that a world independent of my mind exists but I cannot possibly know this. — philosophy

But why is this faith and not inductive logic? We're not positing elephants trumpeting quarks as the basis for everything, or God (unlike Berkeley and Descartes).

But why is this faith and not inductive logic? — Marchesk

I guess it depends how you define ''faith''. Regarding induction, Hume showed that there is no non-circular justification of induction and, as such, induction cannot be justified on rational grounds.

guess it depends how you define ''faith''. — philosophy

I don't define it as induction. I can make inferences that the tree continues to exist in the quad after nobody is perceiving it, but I can't infer that it's God keeping it there.

I can make inferences that the tree continues to exist in the quad after nobody is perceiving it, but I can't infer that it's God keeping it there. — Marchesk

Sure, you can infer that the tree continues to exist independently of your perception of it but it does not follow that you can know this.

The inductive argument would be: ''The tree will persist independently of my perception since it has always done this before.''

And then Hume will ask: ''Why are you using induction?''

''Because induction has worked before...''

Hence circularity.

You're taking a step back instead of answering questions I'm asking and addressing points I'm making.

This: "How do you know that an object can exist independently of perception? You can never know this since it is, by definition, that which is independent of perception, i.e. experience"
Only works as an argument if you're using "know" to refer only to "things that I'm perceiving." In other words, you'd have to be defining "know" as "things that I am perceiving."

Again, why would you use the word "know" to only refer to "things that I am perceiving" ?

If the issue is justification, we can nip that in the bud by the fact that what counts as a justification for anything is subjective.

Again, why would you use the word "know" to only refer to "things that I am perceiving" — Terrapin Station

Sorry, I thought I would have made this clear.

Answer: because ''knowledge'' that is independent of that which you perceive entails knowledge of that which you are not perceiving. To repeat my question: how could you possibly know that which is beyond your perception? You're not perceiving it, hence you cannot know it.

Jesus. It's like you can't learn this part.

Is knowledge defined as "what I am perceiving" ?

There's no need for a condescending tone.

Is knowledge defined as "what I am perceiving" ? — Terrapin Station

I have repeatedly said that perception of an unperceived object is impossible, hence we can have no knowledge of it. Hence, all that I can know are my perceptions (see the Hume quote).

I have repeatedly said that perception of an unperceived object is impossible, — philosophy

Beautiful, but I didn't ask you that.

I asked you this simple yes or no question: Is knowledge defined as "What I am perceiving"?

Answer yes or no or tell me why you can't answer yes or no, where the answer begins with "I cannot answer yes or no because . . ." And then you give the reason.

I literally just wrote in the post above: ''all that I can know are my perceptions''

If that does not answer your question there's not much more I can say. Again, I refer you to the Hume quote:

''We may observe, that 'tis universally allow'd by philosophers, and is besides pretty obvious of itself, that nothing is ever really present with the mind but its perceptions or impressions and ideas, and that external objects become known to us only by those perceptions which they occasion...Now since nothing is ever present to the mind but perceptions...it follows that 'tis impossible for us so much as to conceive or form an idea of any thing specifically different from ideas and impressions.'' [my emphasis]

Beautiful, butI didn't ask you that. — Terrapin Station

If perception of an unperceived object is impossible, and hence I cannot know unperceived objects, then all that I can know are my perceptions.

MF'er.

Yes. No. Or "I cannot answer yes or no because . . ."

It can't be beyond your cognitive abilities to understand and answer a simple yes/no question.

Or at least I can't buy that that could be beyond your cognitive abilities, especially when I'm spending time talking to you about something as complex as idealism vs realism.

''All that I can know are my perceptions''.

Translation: All of my knowledge consists of perceptions.

Is knowledge defined as "What I am perceiving"? — Terrapin Station

Yes. I would have thought that that would follow from ''All of my knowledge consists of perceptions.''

The key word is ''All'' since it means that knowledge cannot take the form of anything other than my perceptions.

Whatever I experience I experience as an idea in my mind. — philosophy

Is this a fact or possibly just a relationship between what we usually mean by 'mind' and 'experience'? If you define experience in terms of mediation, then of course you will never directly experience whatever it is that is being mediated.

On the other hand, we also use 'experience' in terms of experiencing something. And perception means roughly that we are perceiving something. Our rough common sense notion (which is used in-explicitly all the time) is that we live in a shared reality which we experience with some individual variation as a function of our individual spatial position, mood, sense organs, education, etc. If we didn't start from a sense of shared reality, then why are you here trying to tell us something about that shared reality? What can truth mean in the absence of others? In the absence of some vague stuff that makes statements true?
[As an aside, I think all attempts to formalize or make explicit this sense of shared world tend to run into difficulties, but that's an issue for another thread.]

It follows from this that belief in the external world, i.e. a world independent of my experience of it, cannot be based on reason but on faith. — philosophy

If one identifies absolute deductive certainty with reason, then science itself is based not on reason but on faith. An a priori deductive certainty is usually just a matter of definitions (learned in time and imperfectly and not really a priori anyway) (with mathematical intuitions being a little more controversial.) Just about everything is suddenly based on faith rather than reason so that the worth of the distinction is obliterated. And you must then take a leap of faith that you are actually talking to other people and not just figments of your imagination. (I don't think it's controversial that our experience of other people is mediated or indirect.)

In other words, of mind-independent matter I can say nothing at all. — philosophy

In a way yes, but mostly by understanding 'mind-independent matter' in terms of that about which you can say nothing at all (in the first place.) What is discovered is a relationship between meanings as you semi-arbitrarily yank them from the usual blurriness into a specificity that serves your conclusion.

In short, IMV you are just exploring the way we tend to talk rather than some reality beyond that talk. I'm not saying I don't understand you or see why you say what you say.