Can we know that something doesn't exist?

@kennethamy,

kennethamy;136761 wrote:

Yes, it is just vague enough to appeal to you. I was hesitant in posting that for just that reason. Unfortunately, it is also true.

@kennethamy,

kennethamy;136757 wrote:

Ultimately all physical truth is the product of the laws of nature and the initial conditions.

That sounds like mystical nonsense.

@hue-man,

hue-man;131923 wrote:

Can we ever be positively (not absolutely) certain that any particular thing doesn't exist?

in the end no

so whats your point , in the end ?

@kennethamy,

kennethamy;136728 wrote:

Yes. the argument is the one I have already given a number of times.

It is physically impossible for a country with no military forces to win a war against a country with enormous military forces. Luxembourg is a country with no military forces, and China is a country with enormous military forces. I think I will let you draw the conclusion from the two premises.

Night Ripper has shown that premise one is false. In any case, your syllogism would imply logical impossibility, not physical impossibility.

@ughaibu,

ughaibu;136828 wrote:

Night Ripper has shown that premise one is false. In any case, your syllogism would imply logical impossibility, not physical impossibility.

It wouldn't imply a logical impossibility. Logical impossibilities are contradictions, aren't they?

@Zetherin,

Zetherin;136831 wrote:

It wouldn't imply a logical impossibility. Logical impossibilities are contradictions, aren't they?

Well, I assume the contradiction is buried in the definition of "military forces", in conjunction with "war".

@ughaibu,

ughaibu;136832 wrote:

Well, I assume the contradiction is buried in the definition of "military forces", in conjunction with "war".

I think all he's trying to say is that no reasonable person would believe that Luxembourg can win a war against China. It would be impossible for Luxembourg to combat China's troops, if Luxembourg did not have troops to combat with. That seems obvious.

@Zetherin,

Zetherin;136833 wrote:

I think all he's trying to say is that no reasonable person would believe that Luxembourg can win a war against China.

Which says nothing about physical impossibility, it's his opinion, that's all.

Zetherin;136833 wrote:

It would be impossible for Luxembourg to combat China's troops, if Luxembourg did not have troops to combat with. That seems obvious.

What kind of "impossible" is this? And appeals to intuition are not the kind of arguments that can carry a claim about physical impossibility. And this is the point, all that has been offered are statements of personal belief.

@ughaibu,

ughaibu;136834 wrote:

Which says nothing about physical impossibility, it's his opinion, that's all.What kind of "impossible" is this? And appeals to intuition are not the kind of arguments that can carry a claim about physical impossibility. And this is the point, all that has been offered are statements of personal belief.

If I claim that a country has no standing army, and the country has no standing army, this is not simply a statement of personal belief (which you seem to be using synonymously with subjective opinion). It is a statement of fact. It is not simply my personal belief that water is composed of two H molecules and one O molecule. It is true.

Or do you think every statement is an appeal to intuition?

@Zetherin,

Zetherin;136835 wrote:

If I claim that a country has no standing army, and the country has no standing army, this is not simply a statement of personal belief (which you seem to be using synonymously with subjective opinion). It is a statement of fact.

So you are talking about logical impossibility.

@ughaibu,

Zetherin;136833 wrote:

It would be impossible for Luxembourg to combat China's troops, if Luxembourg did not have troops to combat with.

That's logically impossible though, not physically impossible. It's logically impossible for Luxembourg's troops to do anything since Luxembourg's troops don't exist.

@Night Ripper,

Night Ripper;136885 wrote:

That's logically impossible though, not physically impossible. It's logically impossible for Luxembourg's troops to do anything since Luxembourg's troops don't exist.

To be clear, how do you distinguish physical impossibility from logical impossibility? What, technically, does physical impossibility mean? Logical impossibilities are contradiction.

@Zetherin,

Zetherin;136888 wrote:

To be clear, how do you distinguish physical impossibility from logical impossibility? What, technically, does physical impossibility mean? Logical impossibilities are contradiction.

Something is physically impossible if it can't happen even though it's logically possible.

The argument offered thus far is that while there's no logical contradiction implied in going faster than the speed of light, it's still physically impossible to do so.

The problem is, how can you tell if something can't happen rather than simply doesn't happen. In either case it doesn't happen and nothing more can be observed.

@hue-man,

Night Ripper wrote:

Something is physically impossible if it can't happen.

But isn't that what logically impossible means? Contradictions can't happen.

Quote:

The problem is, how can you tell if something can't happen rather than simply doesn't happen

Physical impossibilities are what can't happen, physically, right? So, you are basically saying that we cannot know any physical impossibilities. Isn't that right?

@Zetherin,

Zetherin;136890 wrote:

Contradictions can't happen.

I wouldn't put it like that. There can't exist a "married bachelor" but that's only because a "married bachelor" doesn't refer to anything. It's like saying a prepgwarlik can't exist. It refers to nothing. The concepts of married and bachelor exclude each other. They refer to nothing.

The flip side of your claim would be that tautologies must happen. It will either rain or not rain tomorrow. That's true but it doesn't really say anything about the weather. Logic doesn't deal with existence. It deals with conceivability.

@Night Ripper,

Night Ripper;136893 wrote:

I wouldn't put it like that. There can't exist a "married bachelor" but that's only because a "married bachelor" doesn't refer to anything. It's like saying a prepgwarlik can't exist. It refers to nothing. The concepts of married and bachelor exclude each other. They refer to nothing.

The flip side of your claim would be that tautologies must happen. It will either rain or not rain tomorrow. That's true but it doesn't really say anything about the weather. Logic doesn't deal with existence. It deals with conceivability.

I am not versed enough in logic to be able to appropriately answer your questions, or comment on this matter any further. But I'm sure there are others here that are educated enough. Thanks for the discussion.

@Night Ripper,

Night Ripper;136767 wrote:

That sounds like mystical nonsense.

But it isn't. It is a summary of a particular model of explanation known as the Deductive-Nomological model.

Deductive-nomological model - Wikipedia, the free encyclopedia

---------- Post added 03-06-2010 at 02:12 PM ----------

Night Ripper;136893 wrote:

I wouldn't put it like that. There can't exist a "married bachelor" but that's only because a "married bachelor" doesn't refer to anything. It's like saying a prepgwarlik can't exist. It refers to nothing. The concepts of married and bachelor exclude each other. They refer to nothing.

The flip side of your claim would be that tautologies must happen. It will either rain or not rain tomorrow. That's true but it doesn't really say anything about the weather. Logic doesn't deal with existence. It deals with conceivability.

It is, indeed true, that if a term refers to nothing, then what it refers to does not exist. (A tautology). But it does not follow that if a terms refers to nothing that what it refers to cannot exist. For example, it might be that the term, "extra-terrestrial" refers to nothing, if there are no extra-terrestrials. However, it does not follow that it is impossible that there should be extra-terrestrials. What does not exist could exist. Or, to put it metaphysically, that something is inactual does not imply that it is impossible. Although, of course, the converse is true.

I don't really know what it means to say that logic doesn't deal with existence, so I won't comment on that. You may mean something like that tautologies do not imply that anything exists.

@kennethamy,

kennethamy;136910 wrote:

For example, it might be that the term, "extra-terrestrial" refers to nothing, if there are no extra-terrestrials.

No, again we're back to the same problem of you not understanding the definitions being given to you. The fact that there are no "rivers of cola" in the universe DOES NOT MEAN that "river of cola" doesn't refer to a concept. I can still imagine a river made entirely of cola, so "river of cola" does refer to a concept even if there aren't any that exist.

Words refer to concepts. Concepts are instantiated. There exist no rivers of cola so the concept of a river of cola is not instantiated. Try to understand the the language being used before jumping into the middle of a discussion.

@Night Ripper,

Night Ripper;136918 wrote:

No, again we're back to the same problem of you not understanding the definitions being given to you. The fact that there are no "rivers of cola" in the universe DOES NOT MEAN that "river of cola" doesn't refer to a concept. I can still imagine a river made entirely of cola, so "river of cola" does refer to a concept even if there aren't any that exist.

Words refer to concepts. Concepts are instantiated. There exist no rivers of cola so the concept of a river of cola is not instantiated. Try to understand the the language being used before jumping into the middle of a discussion.

What concept does "square circle" refer to? And what instantiates that concept? I think that Plato held something like your theory of meaning. Only he thought it was Forms that words referred to.

@kennethamy,

kennethamy;136920 wrote:

What concept does "square circle" refer to? And what instantiates that concept?

If you're saying that "square circle" implies a contradiction much like "married bachelor" then you'll get the same analysis as before. It refers to no concept at all and there is no concept to instantiate.

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Can we know that something doesn't exist?

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