Freethought & Rationalism Archive

theophilus · 06-17-2003, 01:25 PM

Quote:

Originally posted by njhartsh
And I've conclusively demonstrated that statement to be false, your semantic quibbling notwithstanding.

But innumberable "universal negatives" can be proved without any "knowledge" (save mere axiomatic definitions) at all; and therefore your point is not "unassailable" but immaterial.

If by proof, you mean a logical demonstration, I don't see that you've proven anything.
The statement "there are no married bachelors" is, as far as I can tell, neither a premise nor a conclusion. It has the form or "No a is non a" and, therefore, has no argumentative value. It is merely a statement of the law of contradiction with the blanks "filled-in."

I could make a million such statement and "prove" nothing:
"There is no water that is not H2O"
"There are no humans that are not homo sapien."

Whatever value such statements may have, they "prove" nothing.

Certainly to suggest that there is some corelation between such tautologies and proving a universal negative with the form
1. If a then not b
2. b
3. Therefore, not a.

Your "arguments" follow the order of
1. All a is a
2. c is a
3. Therefore c is a

I'm impressed.

I had hoped you would notice that I linked to arguments that conclusively prove the first two of my example universal negatives. What an interesting notion of "proof" you must have, if Pythagoras's impeccable mathematical logic does not qualify.

I don't see how these "proofs" have any value in relationship to the logical demonstrations required to prove a universal negative. They are, again, definitional by nature. If you want to say that "there are no right triangles to which the Pythagorian Theorem does not hold," that is unquestionably true, but has no argumentative value.

Proof "by definition" isn't proof? Pray tell, then, how in the world could we ever prove anything? Ever?

Leaving aside the epistemological implications of your question, it cannot be denied that the nature of proof, by definition, differs depending on the thing being proved. You do not prove an argument in the same way you prove that there is a box of crackers in the pantry. Proving something by simply restating the term in different words, e.g., bachelors/unmarried males, is not of the same order as proving that there is no God.

A rather irrelevant attack on the substance of the Argument from Evil, which obviously has nothing to do with my point.

Let's take the following argument:

P1. If there were a god, there would be no sdfoiewr in the world.
P2. There is ample sdfoiewr in the world.
----------------------------
C. There is no god.

I have no interest, on this thread, in addressing whether P1 and P2 are correct. I merely quoted Epicurus to show that the above form of argument is clearly valid--and that this is yet another example (presuming that P1 and P2 are true) of a perfectly legitimate proof of a universal negative.

I do not challenge the validity. As you know, an argument may be valid and entirely false:
1. All men have three legs
2. Socrates is a man
3. Socrates has three legs.

I assumed that when people claim to "prove" a universal negative, they are concerned with something more than triviality. We could multiply formally valide but false arguments and the search for knowledge would not be advanced.

You will be the first person (atheist or theist) I have seen, if you go there, who challenges not only P1 and/or P2 but the validity of deducing C from them. Surely you can't be serious.

- Nathan, by definition

Another universal negative? Of course I can be serious. Epicurius was serious, wasn't he? He was still wrong.

theophilus · 06-17-2003, 01:27 PM

Quote:

Originally posted by njhartsh
And I've conclusively demonstrated that statement to be false, your semantic quibbling notwithstanding.

But innumberable "universal negatives" can be proved without any "knowledge" (save mere axiomatic definitions) at all; and therefore your point is not "unassailable" but immaterial.

If by proof, you mean a logical demonstration, I don't see that you've proven anything.
The statement "there are no married bachelors" is, as far as I can tell, neither a premise nor a conclusion. It has the form or "No a is non a" and, therefore, has no argumentative value. It is merely a statement of the law of contradiction with the blanks "filled-in."

I could make a million such statement and "prove" nothing:
"There is no water that is not H2O"
"There are no humans that are not homo sapien."

Whatever academic value such statements may have, they "prove" nothing.

Certainly to suggest that there is some corelation between such tautologies and proving a universal negative with the form
1. If a then not b
2. b
3. Therefore, not a.

Your "arguments" follow the order of
1. All a is a
2. c is a
3. Therefore c is a

I'm impressed.

I had hoped you would notice that I linked to arguments that conclusively prove the first two of my example universal negatives. What an interesting notion of "proof" you must have, if Pythagoras's impeccable mathematical logic does not qualify.

I don't see how these "proofs" have any value in relationship to the logical demonstrations required to prove a universal negative. They are, again, definitional by nature. If you want to say that "there are no right triangles to which the Pythagorian Theorem does not hold," that is unquestionably true, but has no argumentative value.

Proof "by definition" isn't proof? Pray tell, then, how in the world could we ever prove anything? Ever?

Leaving aside the epistemological implications of your question, it cannot be denied that the nature of proof, by definition, differs depending on the thing being proved. You do not prove an argument in the same way you prove that there is a box of crackers in the pantry. Proving something by simply restating the term in different words, e.g., bachelors/unmarried males, is not of the same order as proving that there is no God.

A rather irrelevant attack on the substance of the Argument from Evil, which obviously has nothing to do with my point.

Let's take the following argument:

P1. If there were a god, there would be no sdfoiewr in the world.
P2. There is ample sdfoiewr in the world.
----------------------------
C. There is no god.

I have no interest, on this thread, in addressing whether P1 and P2 are correct. I merely quoted Epicurus to show that the above form of argument is clearly valid--and that this is yet another example (presuming that P1 and P2 are true) of a perfectly legitimate proof of a universal negative.

I do not challenge the validity. As you know, an argument may be valid and entirely false:
1. All men have three legs
2. Socrates is a man
3. Socrates has three legs.

I assumed that when people claim to "prove" a universal negative, they are concerned with something more than triviality. We could multiply formally valide but false arguments and the search for knowledge would not be advanced.

You will be the first person (atheist or theist) I have seen, if you go there, who challenges not only P1 and/or P2 but the validity of deducing C from them. Surely you can't be serious.

- Nathan, by definition

Another universal negative? Of course I can be serious. Epicurus was serious, wasn't he? He was still wrong.

theophilus · 06-17-2003, 01:56 PM

Quote:

Originally posted by Starseyer
There is a logical fallacy called appeal to ignorance. It relies on the lack of evidence found by an undefined group of people or people who have not conducted a careful systematic (scientific) search for evidence. It goes like this:

All through history people have tried to prove the existance of god(s). No one has definately suceeded. Therefore god(s) do not exist.

Or . . .

Atheists have claimed that there is no God but are unable to prove he doesn't exist. Therefore there is a God.

It wouldn't be a fallacy if there were a qualified group of people (who would they be, anyway?) who performed a systematic search for God (or evidence of god). But since god(s) is a supernatural entity anyway, what would a scientific search prove? God can't be proven or disproven no matter what. As as I see it that makes of the concept of God rather useless.

"Claims that cannot be tested, assertions immune to disproof are veridically worthless, whatever value they they may have in inspiring us or in exciting our sence of wonder." -Carl Sagan, The Demon Haunted World

This quote by Sagan is a classic demonstration of the inability of atheists for follow their own worldview.

First, the statement is self-referentially false, i.e., if "claims that cannot be tested, etc" is true, it is self-defeating. It is an absolute statement which cannot be "tested" or "disproven." It is the nature of an axiom and is "immune to disproof." If it is true, it is false. If it is false, i.e., this statement is an exception to the rule, then it is also false.

It's like saying "there are no absolutes" (except this one).

Second, Sagan was a thoroughgoing materialist. All knowedge is/must be derived from sensation. Well, what sensation is responsible for this statement?

For an interesting perspective on Sagan http://www.trinityfoundation.org/rev...p?ID=068b.html

theophilus · 06-17-2003, 02:21 PM

Quote:

Originally posted by njhartsh
Richard Carrier, a better philosopher than I, makes this same all-too-important point here.

Let's put the "You can't prove a negative" fallacy to sleep!

- Nathan

This is really an excellent article, although it is no support for you. He does not deal at all with the kind of tautological statements you offer.
And, he admits that is the "scope" of negative arguments, i.e., universality that makes them impossible to prove.
He begs off by suggesting a "best guess" alternative to absolute proof, but I don't choose to agree.
His assault on Christianity is, as in most cases, a rank misrepresentation of what the bible actually teaches. It is a caracature of Christian theology filtered through an unbelieving worldview.

Clutch · 06-17-2003, 02:39 PM

Quote:

First, the statement is self-referentially false, i.e., if "claims that cannot be tested, etc" is true, it is self-defeating. It is an absolute statement which cannot be "tested" or "disproven."

No.

Of course Sagan's claim can be tested: Compare intellectual programmes that adopt it as a norm to those that do not, and see which produce more predictive and accurate theories. Why on Earth would you think it untestable? The history of science has already conducted this particular test -- many times over! Sagan's quote summarizes a methodological discovery about how to gather knowledge.

Quote:

Indeed, It is the nature of an axiom and is "immune to disproof."

No. It's "the nature of" a hard-won lesson. Immune to disproof? Entirely your confabulation.

Quote:

Second, Sagan was a thoroughgoing materialist. All knowedge is/must be derived from sensation. Well, what sensation is responsible for this statement?

No. Materialism is just the view that there are no immaterial particulars. You seem to confusing (among other things) materialism for empiricism, and recycling a mangled version of an old objection to positivistic verificationism. (Which was a lousy objection even in the right context and before the mangling.)

Perhaps you should get at least the basics straight before accusing Sagan of error.

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