proving a negative

[petesampras]

You said - "We can guess that something might exist, but without observations to back up those hypothesis, that's all they are. Guesses."

Which was said in the context of my assertion that we could know that a fruit will exist at some point without ever observing it. I gave an example of how you could know something exists without directly observing it. If you see a flaw in this example can you point it out. To me it implies that we can know that something exists without directly observing it.

I never said they had to be directly observed, you did. The key is whether or not it can be independently verified, which I added in my next post.

Ghetto edit: In other words, as long as someone can repeat the observations when they know the information that someone else directly observed, then direct observation is not necessary as long as someone somewhere has done so and given sufficient information to determine what the exact object is by someone who's never seen it.

Ok, this is where I disagree with you again. . Specifically - "direct observation is not necessary as long as someone somewhere has done so". Direct observation is not necessary. I find a new type of fruit - I know a new species of plant exists that gave rise to it. Direct observation is not needed to say this.

[Darth Servo]

Thats like saying the finding a new fossil doesn't constitute direct observation of a new species. The fossil is (or I guess I should say 'was') a part of the animal's body, just as the piece of fruit was part of the plant.

[petesampras]

Thats like saying the finding a new fossil doesn't constitute direct observation of a new species. The fossil is (or I guess I should say 'was') a part of the animal's body, just as the piece of fruit was part of the plant.

Ok, but the point of mine that, I believe, Zod is objecting to is the idea we can know a fruit will exist from only studying the tree when it is not producing fruit.

[General Zod]

Thats like saying the finding a new fossil doesn't constitute direct observation of a new species. The fossil is (or I guess I should say 'was') a part of the animal's body, just as the piece of fruit was part of the plant.

Ok, but the point of mine that, I believe, Zod is objecting to is the idea we can know a fruit will exist from only studying the tree when it is not producing fruit.

Uhm, no. The point I'm objecting to is that something cannot be known without observations. You continue to claim otherwise then contradict yourself by using examples involving observations.

[Feil]

Chrissakes. A datum is not a hypothesis. A speculative datum is not a hypothesis. A hypothesis is an explanation of data. It may or may not end with a speculative datum.


This is right:
"Data: This flowering plant is known to be pollinated by insects that are attracted to bright colors.
Hypothesis: When it flowers, the flowers are brightly colored."


This is wrong:
"Data: This flowering plant exists.
Hypothesis: When it flowers, the flowers are brightly colored."

See the difference?

[petesampras]

Chrissakes. A datum is not a hypothesis. A speculative datum is not a hypothesis. A hypothesis is an explanation of data. It may or may not end with a speculative datum.


This is right:
"Data: This flowering plant is known to be pollinated by insects that are attracted to bright colors.
Hypothesis: When it flowers, the flowers are brightly colored."


This is wrong:
"Data: This flowering plant exists.
Hypothesis: When it flowers, the flowers are brightly colored."

See the difference?

Yes, in one case the data supports the hypothesis, in the other case it does not. A hypothesis does not, however, require the existance of supporting data to be a hypothesis. It requires supporting data to verify it. These are two completely seperate concepts.

[Darth Wong]

Yes, in one case the data supports the hypothesis, in the other case it does not. A hypothesis does not, however, require the existance of supporting data to be a hypothesis. It requires supporting data to verify it. These are two completely seperate concepts.

You are confusing useful hypotheses and useless ones. The fact that you can still call a useless hypothesis a hypothesis does not change anything; it only means that you are desperately trying to save an original point which is also, not coincidentally, totally useless.

[petesampras]

Thats like saying the finding a new fossil doesn't constitute direct observation of a new species. The fossil is (or I guess I should say 'was') a part of the animal's body, just as the piece of fruit was part of the plant.

Ok, but the point of mine that, I believe, Zod is objecting to is the idea we can know a fruit will exist from only studying the tree when it is not producing fruit.

Uhm, no. The point I'm objecting to is that something cannot be known without observations. You continue to claim otherwise then contradict yourself by using examples involving observations.

I have not contradicted myself at any point to my knowledge - care to provide specific quotes?

You originally objected to my assertion that is possible to know that a type of fruit exists without ever anyone directly observing it. If you don't object to this, I'm not sure what you are objecting to exactly.

[General Zod]

Chrissakes. A datum is not a hypothesis. A speculative datum is not a hypothesis. A hypothesis is an explanation of data. It may or may not end with a speculative datum.


This is right:
"Data: This flowering plant is known to be pollinated by insects that are attracted to bright colors.
Hypothesis: When it flowers, the flowers are brightly colored."


This is wrong:
"Data: This flowering plant exists.
Hypothesis: When it flowers, the flowers are brightly colored."

See the difference?

Yes, in one case the data supports the hypothesis, in the other case it does not. A hypothesis does not, however, require the existance of supporting data to be a hypothesis. It requires supporting data to verify it. These are two completely seperate concepts.

A hypothesis with no data whatsoever is what we like to call speculation, which is usually worthless.

[Darth Wong]

You originally objected to my assertion that is possible to know that a type of fruit exists without ever anyone directly observing it. If you don't object to this, I'm not sure what you are objecting to exactly.

Don't change the subject, asshole. If you think that you can save your "you don't need evidence to make a claim" nonsense by creating an example where you have indirect evidence for that claim, you're either stupid or you're dishonest.

[Feil]

Are you trying to be stupid, or does it come to you naturally?

Dictionary.com:

a proposition, or set of propositions, set forth as an explanation for the occurrence of some specified group of phenomena, either asserted merely as a provisional conjecture to guide investigation (working hypothesis) or accepted as highly probable in the light of established facts.

American Heritage Dictionary:

A tentative explanation for an observation, phenomenon, or scientific problem that can be tested by further investigation.

American Heritage Dictionary of Cultural Literacy:

In science, a statement of a possible explanation for some natural phenomenon. A hypothesis is tested by drawing conclusions from it; if observation and experimentation show a conclusion to be false, the hypothesis must be false.

The second one is not a hypothesis.

[Feil]

Above post in reply to petesampras, sorry.

[General Zod]

Are you trying to be stupid, or does it come to you naturally?

Dictionary.com:

a proposition, or set of propositions, set forth as an explanation for the occurrence of some specified group of phenomena, either asserted merely as a provisional conjecture to guide investigation (working hypothesis) or accepted as highly probable in the light of established facts.

American Heritage Dictionary:

A tentative explanation for an observation, phenomenon, or scientific problem that can be tested by further investigation.

American Heritage Dictionary of Cultural Literacy:

In science, a statement of a possible explanation for some natural phenomenon. A hypothesis is tested by drawing conclusions from it; if observation and experimentation show a conclusion to be false, the hypothesis must be false.

The second one is not a hypothesis.

And just for petesempras sake, so we're all on the same page:

Main Entry: 1know
Pronunciation: 'nO
Function: verb
Inflected Form(s): knew /'nü also 'nyü/; known /'nOn/; know·ing
Etymology: Middle English, from Old English cnAwan; akin to Old High German bichnAan to recognize, Latin gnoscere, noscere to come to know, Greek gignOskein
transitive verb
1 a (1) : to perceive directly : have direct cognition of (2) : to have understanding of <importance of knowing oneself> (3) : to recognize the nature of : DISCERN b (1) : to recognize as being the same as something previously known (2) : to be acquainted or familiar with (3) : to have experience of
2 a : to be aware of the truth or factuality of : be convinced or certain of b : to have a practical understanding of <knows how to write>

The bolded bit is the important one.

[petesampras]

Are you trying to be stupid, or does it come to you naturally?

Dictionary.com:

a proposition, or set of propositions, set forth as an explanation for the occurrence of some specified group of phenomena, either asserted merely as a provisional conjecture to guide investigation (working hypothesis) or accepted as highly probable in the light of established facts.

American Heritage Dictionary:

A tentative explanation for an observation, phenomenon, or scientific problem that can be tested by further investigation.

American Heritage Dictionary of Cultural Literacy:

In science, a statement of a possible explanation for some natural phenomenon. A hypothesis is tested by drawing conclusions from it; if observation and experimentation show a conclusion to be false, the hypothesis must be false.

The second one is not a hypothesis.

Fine, I concede that the official definitions of hypothesis provided do, evidently, require the prior existance of some data or phemonenon to explain.

I'm not sure, however, how, for example, the search for planets around other star systems would fit into this definition. It is not an attempt to explain existing phenomena. It is speculating that something may exist and then searching for it.

[General Zod]

Fine, I concede that the official definitions of hypothesis provided do, evidently, require the prior existance of some data or phemonenon to explain.

I'm not sure, however, how, for example, the search for planets around other star systems would fit into this definition. It is not an attempt to explain existing phenomena. It is speculating that something may exist and then searching for it.

If you find data that supports your speculation, then you can use the data to create a hypothesis refining that explanation. I don't see a problem here.

[Feil]

I'm not sure, however, how, for example, the search for planets around other star systems would fit into this definition. It is not an attempt to explain existing phenomena. It is speculating that something may exist and then searching for it.

We would have to be fools to hypothesize the existence of a planet orbiting every star. This is where the default negative view comes in: we assume that there is no planet until we have evidence of a planet.

Once we have evidence of a planet (periodic gravitational distortions, periodic momentary dimming of light, etc) we hypothesize the existence of a planet to explain that evidence, and look for other evidence to support the existence of our hypothesized planet; we also look for evidence that would indicate the nonexistence of a planet, or which would make the planet hypothesis no more likely than other hypotheses.

[petesampras]

Fine, I concede that the official definitions of hypothesis provided do, evidently, require the prior existance of some data or phemonenon to explain.

I'm not sure, however, how, for example, the search for planets around other star systems would fit into this definition. It is not an attempt to explain existing phenomena. It is speculating that something may exist and then searching for it.

If you find data that supports your speculation, then you can use the data to create a hypothesis refining that explanation. I don't see a problem here.

Fair enough.

What then, would you call a testable 'assertion' that does not yet have any supporting data and is not an attempt to explain existing data.

Say if I assert that a pyramid of particular dimensions can sharpen razor blades left in it over night. That can be tested empirically. I'm just curious as to what that type of statement would be. I would have called it a hypothesis, but clearly that doesn't fit in with the definitions provided.

[Darth Wong]

I'm not sure, however, how, for example, the search for planets around other star systems would fit into this definition. It is not an attempt to explain existing phenomena. It is speculating that something may exist and then searching for it.

The act of searching for something is not a hypothesis, and no one ever said that it was.

[General Zod]

Fine, I concede that the official definitions of hypothesis provided do, evidently, require the prior existance of some data or phemonenon to explain.

I'm not sure, however, how, for example, the search for planets around other star systems would fit into this definition. It is not an attempt to explain existing phenomena. It is speculating that something may exist and then searching for it.

If you find data that supports your speculation, then you can use the data to create a hypothesis refining that explanation. I don't see a problem here.

Fair enough.

What then, would you call a testable 'assertion' that does not yet have any supporting data and is not an attempt to explain existing data.

Say if I assert that a pyramid of particular dimensions can sharpen razor blades left in it over night. That can be tested empirically. I'm just curious as to what that type of statement would be. I would have called it a hypothesis, but clearly that doesn't fit in with the definitions provided.

Since it doesn't actually explain anything, it would be speculation. We've gone over this already.

[Kuroneko]

Since the original question has been answered adequately, please excuse my digression to something trivial and yet counter to the intuitions of most people, and hence (hopefully) interesting.

The flip side of the coin is that although a negative cannot be proved, it can be strongly [confirmed]. If you go out and make a worldwide survey of crows, collecting a large random sample of crows, then a non-white crow, if it exists has a fair chance of making it into our sample, and therefore demonstrate its existence and disproving our assertion that there is no non-black crow. ...

I'm not sure that there is a distinction between "proved" and "strongly confirmed", unless of course the former refers to the absolute kind. But in any case, just to do the same thing a bit differently: by the law of transposition,
"All crows are black" = (All x)(x is Crow → x is Black) = (All x)(x is not-Black → x is not-Crow)
Thus, the observation of any non-black non-crow is evidence that all crows are black. Thus, red trucks are evidence for the claim that all crows are black. There is a difference in degree of confirmation, of course, otherwise there is no problem.

[Wyrm]

Since the original question has been answered adequately, please excuse my digression to something trivial and yet counter to the intuitions of most people, and hence (hopefully) interesting.

The flip side of the coin is that although a negative cannot be proved, it can be strongly [confirmed]. If you go out and make a worldwide survey of crows, collecting a large random sample of crows, then a non-white crow, if it exists has a fair chance of making it into our sample, and therefore demonstrate its existence and disproving our assertion that there is no non-black crow. ...

I'm not sure that there is a distinction between "proved" and "strongly confirmed", unless of course the former refers to the absolute kind.

Yes. Perhaps "supported" is a better word than "confirmed".

But in any case, just to do the same thing a bit differently: by the law of transposition,
"All crows are black" = (All x)(x is Crow → x is Black) = (All x)(x is not-Black → x is not-Crow)
Thus, the observation of any non-black non-crow is evidence that all crows are black. Thus, red trucks are evidence for the claim that all crows are black. There is a difference in degree of confirmation, of course, otherwise there is no problem.

Yep. And this is where Bayes's rule can tell you the degree of confirmation, provided we believe confidence in a hypothesis can be quantified as a probability. In a world of many non-black things, observing a red truck is only weak support for the hypothesis that all crows are black. This is because there are many non black things in the world, so observing a non-black non-crow is confirmation of our hypothesis, but not all that remarkable confirmation. On the other hand, in the World of Pitch Black Things, where almost everything is colored black, except for that lonesome red truck, then observing the red truck is strong evidence indeed for the hypothesis.

[Feil]

While all this [Kuroneko's post and down] is true (and I don't see why it would be counterintuitive, though that might be because my father introduced it to me when I was a wee little lad)--is there a practical application to any of it? IE, "Okay, so it's evidence for all crows being black; it's also evidence for all crows being from Proxima Centuri."

[Kuroneko]

While all this is true (and I don't see why it would be counterintuitive, though that might be because my father introduced it to me when I was a wee little lad)--is there a practical application to any of it?

Not really--it is too trivial, although by the amount of literature written on this inductive paradox (usually with ravens rather than crows), it is indeed seen as counterintuitive by many. The only semi-practical uses of this is illustrating the the extreme sensitivity of the principle of induction to background information (something made more explicit in Bayesianism) and the very common-sense notion that we can also confirm our hypothesis by making a random sample of all things, rather than a random sample of just ravens.

[Edi]

The crow is not really a useful example for something that is all black.



Much better images

That there is Cornix Corvus corone, the common crow in these parts. We call it just 'crow', but it is sometimes called 'gray crow' to distinguish it from the various subspecies in other parts of the world that tend to be uniformly black.

Now, if you were to be looking for an albino crow of whatever variety...

[Keevan_Colton]

You can only ever prove a negative by exclusion, you can show something doesnt exist via an observation that is incompatible with its existence. The whole "there is no 'e' there" thing, you are proving that there is no e there by observing its absence...the absence of 'e' is the observation.

So long as you give something definite parameters, it can in principle be proven false by finding an observation that contradicts the parameters of the object. This is the very basic notion of falsifiability that science and every single tiny scrap of human advancement and knowledge is based upon...

It is still a positive that proves things though.