1 of 3
1
Logical fallacy
Posted: 03 January 2009 04:51 AM   [ Ignore ]
Sr. Member
RankRankRankRankRankRankRankRankRank
Total Posts:  252
Joined  2007-07-12

Hi.

Is the correct definition of a logical fallacy

“An argument, in which the premises do not support the conclusion”?

If so, then an argument of the type

“X is true, therefore
X is true”

does not have a logical fallacy.

Profile
 
 
Posted: 03 January 2009 08:59 AM   [ Ignore ]   [ # 1 ]
Administrator
Avatar
RankRankRankRankRankRankRankRankRankRank
Total Posts:  15435
Joined  2006-02-14

Right. “Begging the question” is not a logical fallacy. There are some who seem to assume they have a knock-down argument when they can accuse someone of “begging the question”. But this accusation has no implications whatever about the validity or soundness of the argument being presented. Indeed, perfectly valid arguments are guaranteed to beg the question:

If A then B
A

———-
B

If this is true, then what is the problem with “begging the question”? “Begging the question” is a fallacy of argumentation, not of logic. That is, it is an implicit rejection of continued argument. It is to say, “I consider that a posit from which I begin, and which itself needs no further logical or evidentiary support.”

The problem comes when what is being posited is itself open to persuasive counter-argument.

Every argument structure must either be infinitely long (hence not humanly graspable) or must end in certain basic posits which are themselves unsupported. If the argument structure is to be sound, those unsupported posits must themselves be true. If the argument structure is to be convincing, those unsupported posits must be obvious, or in the words of the Declaration of Independence, self-evident.

(Note: there is no potential posit which is literally self-evident to everyone. So something’s being self-evident only makes it convincing; strictly speaking, being self-evident or not has no bearing on truth).

At any rate, “begging the question” only becomes a problem if one takes as one’s posit something which is not only not self-evident, but which good arguments exist for why it is false. E.g., one can begin with the posit that God exists. Or one can begin with the posit that the Bible is literally true. Both of these are posits which are very popular in theology, and both of them “beg the question” in the bad sense, since these are controversial claims which admit of detailed refutation. (Of course, in other branches of theology they may be supported by further argument and not be posits).

 Signature 

Doug

-:- -:—:- -:—:- -:—:- -:—:- -:—:-

El sueño de la razón produce monstruos

Profile
 
 
Posted: 03 January 2009 10:44 AM   [ Ignore ]   [ # 2 ]
Sr. Member
Avatar
RankRankRankRankRankRankRankRankRankRank
Total Posts:  3349
Joined  2007-11-21
wandering - 03 January 2009 04:51 AM

Hi.

Is the correct definition of a logical fallacy

“An argument, in which the premises do not support the conclusion”?

If so, then an argument of the type

“X is true, therefore
X is true”

does not have a logical fallacy.


Though the conclusion follows from the premise, the argument is fallacious because it begs the question.  The argument does not represent a logical inference that would assist one in believing that X is true if one did not already explicitly believe that X is true.
Circulus in demonstrando:  circular reasoning.

Logical fallacy may also be defined as an error in reasoning, and with that understanding we can look at the definition you provided with greater understanding.  What does it mean to “support” a conclusion?  Though it is inarguably true that the truth of X follows from the truth of X (formal validity), the truth of X does not in any non-trivial way support the truth of X in the sense of providing a rationale for believing the truth of X in the first place.

Profile
 
 
Posted: 03 January 2009 10:45 AM   [ Ignore ]   [ # 3 ]
Sr. Member
Avatar
RankRankRankRankRankRankRankRankRankRank
Total Posts:  3349
Joined  2007-11-21
dougsmith - 03 January 2009 08:59 AM

Right. “Begging the question” is not a logical fallacy.

Sure it is.  It just isn’t a formal fallacy.

The following might be of interest in terms of this dispute:

http://www.johnwoods.ca/Begging the Question is Not a Fallacy.pdf

Well that’s odd.  The forum alters the URL, rendering it invalid.  You can get there from here with a little bit of effort:
http://en.wikipedia.org/wiki/Begging_the_question

[ Edited: 03 January 2009 11:11 AM by Bryan ]
Profile
 
 
Posted: 03 January 2009 12:18 PM   [ Ignore ]   [ # 4 ]
Moderator
RankRankRankRankRankRankRankRankRankRank
Total Posts:  5508
Joined  2006-10-22

I don’t know where this fits in the set of logical or other kinds of fallacies, but it would seem that the proposed statement and conclusion fail Popper’s principle of falsifiability.

Occam

Profile
 
 
Posted: 03 January 2009 12:26 PM   [ Ignore ]   [ # 5 ]
Administrator
Avatar
RankRankRankRankRankRankRankRankRankRank
Total Posts:  15435
Joined  2006-02-14

By “logical fallacy” I mean a “formal fallacy”, i.e. a fallacy of formal logic. “Begging the question” is not a fallacy of formal logic.

 Signature 

Doug

-:- -:—:- -:—:- -:—:- -:—:- -:—:-

El sueño de la razón produce monstruos

Profile
 
 
Posted: 03 January 2009 01:50 PM   [ Ignore ]   [ # 6 ]
Sr. Member
Avatar
RankRankRankRankRankRankRankRankRankRank
Total Posts:  3349
Joined  2007-11-21
dougsmith - 03 January 2009 12:26 PM

By “logical fallacy” I mean a “formal fallacy”, i.e. a fallacy of formal logic. “Begging the question” is not a fallacy of formal logic.

I recall you used the term (“fallacy”) as a stand-in for “formal fallacy” weeks ago, so the POV as you expressed it didn’t surprise me.  The paper I linked makes an argument that begging the question isn’t a fallacy at all, but sifts through semantics in a somewhat tortured manner, in my opinion.

I have had people argue that I should accept X on the basis of a flatly circular argument when they know full well I don’t accept the premise.  The author calls that “flawed argument” a type of stupidity that doesn’t meet the traditional understanding of fallacy.  It’s an interesting argument, but I don’t quite buy it.

Profile
 
 
Posted: 03 January 2009 02:17 PM   [ Ignore ]   [ # 7 ]
Administrator
Avatar
RankRankRankRankRankRankRankRankRankRank
Total Posts:  15435
Joined  2006-02-14
Bryan - 03 January 2009 01:50 PM

I have had people argue that I should accept X on the basis of a flatly circular argument when they know full well I don’t accept the premise.  The author calls that “flawed argument” a type of stupidity that doesn’t meet the traditional understanding of fallacy.  It’s an interesting argument, but I don’t quite buy it.

When one argues with someone for long enough, it tends to happen that one figures out which the posits are about which one disagrees. Then each of the protagonists can accuse the other of “begging the question” with respect to those posits.

That is, unless they wish the argument to go on forever, and continue providing arguments for each of the posits that they hold. But this usually becomes tiresome, and at any rate there are certain posits (like the validity of modus ponens) which literally cannot themselves be given non-circular justifications.

Let’s say I’m arguing with someone who doesn’t accept the premise that logic is truth-preserving. (I have in fact had arguments with people who claimed that logic was self-refuting, believe it or not). There is no way I will not “beg the question” in arguing with such a person, at least by his lights. But that doesn’t mean my argument isn’t valid and sound.

What one has to say eventually in an argument is that we disagree about the plausibility of a given premise, and if you have no further arguments as to why I should accept that premise, then our argument is over. The same thing happens when one presents one’s opponent with a reductio ad absurdum and ... he accepts it. The argument is over. By my lights he’s lost. By his lights he’s fine. But there’s nothing more to be said between us, since by my lights his position is absurd.

Here’s again where we distinguish between epistemology and metaphysics, or opinion and truth.

 Signature 

Doug

-:- -:—:- -:—:- -:—:- -:—:- -:—:-

El sueño de la razón produce monstruos

Profile
 
 
Posted: 04 January 2009 03:30 AM   [ Ignore ]   [ # 8 ]
Sr. Member
RankRankRankRankRankRankRankRankRank
Total Posts:  252
Joined  2007-07-12
dougsmith - 03 January 2009 08:59 AM

Right. “Begging the question” is not a logical fallacy. There are some who seem to assume they have a knock-down argument when they can accuse someone of “begging the question”. But this accusation has no implications whatever about the validity or soundness of the argument being presented. Indeed, perfectly valid arguments are guaranteed to beg the question:

If A then B
A

———-
B

If this is true, then what is the problem with “begging the question”? “Begging the question” is a fallacy of argumentation, not of logic. That is, it is an implicit rejection of continued argument. It is to say, “I consider that a posit from which I begin, and which itself needs no further logical or evidentiary support.”

Do you have a rigorous definition for what “a fallacy of argumentation” is?

The problem comes when what is being posited is itself open to persuasive counter-argument.

Every argument structure must either be infinitely long (hence not humanly graspable) or must end in certain basic posits which are themselves unsupported. If the argument structure is to be sound, those unsupported posits must themselves be true. If the argument structure is to be convincing, those unsupported posits must be obvious, or in the words of the Declaration of Independence, self-evident.

(Note: there is no potential posit which is literally self-evident to everyone. So something’s being self-evident only makes it convincing; strictly speaking, being self-evident or not has no bearing on truth).

At any rate, “begging the question” only becomes a problem if one takes as one’s posit something which is not only not self-evident, but which good arguments exist for why it is false. E.g., one can begin with the posit that God exists. Or one can begin with the posit that the Bible is literally true. Both of these are posits which are very popular in theology, and both of them “beg the question” in the bad sense, since these are controversial claims which admit of detailed refutation. (Of course, in other branches of theology they may be supported by further argument and not be posits).

According to what you have written, I do not see a need to introduce additional concepts than validity and soundness. “Begging the question” is a case of an argument when the soundness is not established, while the argumentor pretends that it is.

Profile
 
 
Posted: 04 January 2009 03:33 AM   [ Ignore ]   [ # 9 ]
Sr. Member
RankRankRankRankRankRankRankRankRank
Total Posts:  252
Joined  2007-07-12

I have another issue with regards to logical fallacies .

When someone argues

“X is true because A says so”,

it is usually adressed as “fallacy from authority”.

But we canv view it as an argument with an implicit premise

“A says X
implicit premise: everything A says is true.
X is true”.

And thus the argument is perfectly valid.

Is it sound? One might claim that the soundness of it is an empirical question - is indeed everything A say true. Therefore, it appears, according to this line of reasoninf that such arguments cannot be dismissed out of hand, but the nature of A has to be checked.

(Not sure I really agree with this extreme, but I will see how you respond)

Profile
 
 
Posted: 04 January 2009 03:34 AM   [ Ignore ]   [ # 10 ]
Sr. Member
RankRankRankRankRankRankRankRankRank
Total Posts:  252
Joined  2007-07-12

__

[ Edited: 04 January 2009 05:34 AM by wandering ]
Profile
 
 
Posted: 04 January 2009 09:18 AM   [ Ignore ]   [ # 11 ]
Administrator
Avatar
RankRankRankRankRankRankRankRankRankRank
Total Posts:  15435
Joined  2006-02-14
wandering - 04 January 2009 03:30 AM

Do you have a rigorous definition for what “a fallacy of argumentation” is?

I don’t have one readily to hand, no. But it is an “informal fallacy”, not a fallacy of formal logic. It is a fallacy in that even though the argument as presented is (or may be) in logically valid form, nevertheless it is unconvincing. In this case, it is unconvincing because there are premises that are questionable but unsupported.

Now, the main issue here is whether these premises really are questionable. A separate but associated question is whether the premises, though questionable, are nonetheless true.

E.g.: someone who claims that deduction is not truth-preserving appears to believe that the premise that deduction preserves truth is itself questionable. It is not.

E.g.: someone long ago may have made an argument that included the premise that the world was round. To his audience this premise would have been questionable. But even though he was “begging the question”, his argument would in fact have been valid and sound.

wandering - 04 January 2009 03:30 AM

According to what you have written, I do not see a need to introduce additional concepts than validity and soundness. “Begging the question” is a case of an argument when the soundness is not established, while the argumentor pretends that it is.

Well, but in putting it that way you are introducing the additional concept of something’s “being established”, where this is clearly more than merely a matter of validity or soundness, since it is a property of premises in isolation.

 Signature 

Doug

-:- -:—:- -:—:- -:—:- -:—:- -:—:-

El sueño de la razón produce monstruos

Profile
 
 
Posted: 04 January 2009 09:27 AM   [ Ignore ]   [ # 12 ]
Administrator
Avatar
RankRankRankRankRankRankRankRankRankRank
Total Posts:  15435
Joined  2006-02-14
wandering - 04 January 2009 03:33 AM

I have another issue with regards to logical fallacies .

When someone argues

“X is true because A says so”,

it is usually adressed as “fallacy from authority”.

But we canv view it as an argument with an implicit premise

“A says X
implicit premise: everything A says is true.
X is true”.

And thus the argument is perfectly valid.

Is it sound? One might claim that the soundness of it is an empirical question - is indeed everything A say true. Therefore, it appears, according to this line of reasoninf that such arguments cannot be dismissed out of hand, but the nature of A has to be checked.

(Not sure I really agree with this extreme, but I will see how you respond)

You don’t need quite such a strong implicit premise. You could, for example, have something like this:

(1) A says X
(2) X is a claim about Y
(3) A is an expert in Y
(4) Experts are always (? or mostly always?) right about claims in their expertise
(5) Therefore A is always (? or mostly always?) right about claims about Y
(6) Therefore A is right (? or almost certainly right?) about X

The problem is that reformulating an argument logically doesn’t make it any stronger. It simply makes clear where the weak premises are. Clearly, (4) is the problem here, and certainly your “implicit premise” is false.

NB: I am not claiming that (4) is false; in fact, I think it’s problematic but intriguing. The “fallacy from authority” isn’t really much of a fallacy IMO, although it can be proper in some instances. The problem about arguments from authority isn’t so much that (4) is false; it’s rather that wherever an authority can be elicited in some argument, the argument that authority provides can be elicited as well, and dissected.

A secondary problem is that there are many, many areas in which there are no real authorities in the sense of (4), since there is so much deep disagreement as to what is right and wrong.

 Signature 

Doug

-:- -:—:- -:—:- -:—:- -:—:- -:—:-

El sueño de la razón produce monstruos

Profile
 
 
Posted: 04 January 2009 09:30 AM   [ Ignore ]   [ # 13 ]
Sr. Member
RankRankRankRankRankRankRankRankRank
Total Posts:  252
Joined  2007-07-12
dougsmith - 04 January 2009 09:27 AM
wandering - 04 January 2009 03:33 AM

I have another issue with regards to logical fallacies .

When someone argues

“X is true because A says so”,

it is usually adressed as “fallacy from authority”.

But we canv view it as an argument with an implicit premise

“A says X
implicit premise: everything A says is true.
X is true”.

And thus the argument is perfectly valid.

Is it sound? One might claim that the soundness of it is an empirical question - is indeed everything A say true. Therefore, it appears, according to this line of reasoninf that such arguments cannot be dismissed out of hand, but the nature of A has to be checked.

(Not sure I really agree with this extreme, but I will see how you respond)

You don’t need quite such a strong implicit premise. You could, for example, have something like this:

(1) A says X
(2) X is a claim about Y
(3) A is an expert in Y
(4) Experts are always (? or mostly always?) right about claims in their expertise
(5) Therefore A is always (? or mostly always?) right about claims about Y
(6) Therefore A is right (? or almost certainly right?) about X

The problem is that reformulating an argument logically doesn’t make it any stronger. It simply makes clear where the weak premises are. Clearly, (4) is the problem here, and certainly your “implicit premise” is false.

The crux of my problem is that an argument that fails for a reason of logic, and one that fails for reason of soundness are two very different types of an argument. However, by merely reformulating it, I changed its nature completely.

Profile
 
 
Posted: 04 January 2009 09:46 AM   [ Ignore ]   [ # 14 ]
Sr. Member
Avatar
RankRankRankRankRankRankRankRankRankRank
Total Posts:  3349
Joined  2007-11-21
dougsmith - 04 January 2009 09:18 AM
wandering - 04 January 2009 03:30 AM

Do you have a rigorous definition for what “a fallacy of argumentation” is?

I don’t have one readily to hand, no. But it is an “informal fallacy”, not a fallacy of formal logic. It is a fallacy in that even though the argument as presented is (or may be) in logically valid form, nevertheless it is unconvincing. In this case, it is unconvincing because there are premises that are questionable but unsupported.

Now, the main issue here is whether these premises really are questionable. A separate but associated question is whether the premises, though questionable, are nonetheless true.

E.g.: someone who claims that deduction is not truth-preserving appears to believe that the premise that deduction preserves truth is itself questionable. It is not.

E.g.: someone long ago may have made an argument that included the premise that the world was round. To his audience this premise would have been questionable. But even though he was “begging the question”, his argument would in fact have been valid and sound.

Whoa, there.  You wrote hastily, for there is no barrier to creating an invalid argument for the spheroid shape of the Earth, including one that contains the true premise that the earth is spheroid in shape.  I have little doubt that you agree with that, but your sentence conveys the opposite impression.

In my opinion, the error in reasoning is implicit in the presentation of an argument that is intended to convince others of the conclusion.  It is not reasonable to convince somebody of the truth of a conclusion by using that very conclusion as a premise in a circular argument recommending the conclusion in turn.

wandering - 04 January 2009 03:30 AM

According to what you have written, I do not see a need to introduce additional concepts than validity and soundness. “Begging the question” is a case of an argument when the soundness is not established, while the argumentor pretends that it is.

Well, but in putting it that way you are introducing the additional concept of something’s “being established”, where this is clearly more than merely a matter of validity or soundness, since it is a property of premises in isolation.

That’s a good point if he is, in fact, introducing that type of concept.  I take “wandering” as saying essentially the same thing I’m saying, however.  It is not reasonable to use a manifestly contested premise to convince one’s opposite of the truth of a conclusion, and I would count that as an error of reasoning in itself.  That error is implicit in the argument itself given the context (oftimes, anyway).  It’s one thing to present an argument for discussion, as with one using made-up words that nonetheless is valid if the words are assumed not to change meaning.  It is another thing to expect somebody else to accept the conclusion as true based on the argument (that is, to accept it as a sound argument and not merely as valid).

Just an example, for fun:

P1 The Earth is round.
P2 A round Earth makes candy taste good.
C: Therefore,
The Earth is round.

[ Edited: 04 January 2009 09:54 AM by Bryan ]
Profile
 
 
Posted: 04 January 2009 09:50 AM   [ Ignore ]   [ # 15 ]
Administrator
Avatar
RankRankRankRankRankRankRankRankRankRank
Total Posts:  15435
Joined  2006-02-14
wandering - 04 January 2009 09:30 AM

The crux of my problem is that an argument that fails for a reason of logic, and one that fails for reason of soundness are two very different types of an argument. However, by merely reformulating it, I changed its nature completely.

OK.

 Signature 

Doug

-:- -:—:- -:—:- -:—:- -:—:- -:—:-

El sueño de la razón produce monstruos

Profile
 
 
   
1 of 3
1