Is pointing out logical fallacies sufficient to refute an argument?

[Silentknight]

A fallacy as you all know is defined as a component of an argument which, being demonstrably flawed in its logic or form, renders the argument invalid in whole, or as an argument using false or invalid inference. One of the more common debate tactics around here is to point out the logical fallacies in an argument being presented, as a means of demonstrating that the argument as a whole is invalid. It seems pretty clear to me that exposing the flawed logic that an argument is based on both addresses the argument and refutes said argument.

However, it has recently come to my attention that there are apparently types of "logic" by means of which an argument can not only commit, but also include fallacies as an integral part of its form, which somehow renders it irrefutable. This seems to be especially true of arguments in which the conclusion is assumed in the premises, or where everything but the conclusion one is aiming for is defined out of existence. I probably missed something in the Logic 101 class I took a couple of semesters ago, or in my online research into informal fallacies, but how is begging the question ever a valid form of reasoning?

I suppose my next question would be, is there really a school of logic that ignores or is somehow exempt from these basic rules? Where A + B = A is considered a syllogism? Where one can propose categories that only accomodate a single member? Where a fallacy-riddled argument can be deemed untouchable?

Should I be prepared to revise my entire way of thinking and accept that the following sources don't know what they're talking about?

http://web.cn.edu/kwheeler/fallacies_list.html
http://philosophy.lander.edu/logic/syll_fall.html
http://www.unc.edu/depts/wcweb/handouts/fallacies.html
http://en.wikipedia.org/wiki/List_of_fallacies
http://www.fallacyfiles.org/

[Robin]

A fallacy as you all know is defined as a component of an argument which, being demonstrably flawed in its logic or form, renders the argument invalid in whole, or as an argument using false or invalid inference. One of the more common debate tactics around here is to point out the logical fallacies in an argument being presented, as a means of demonstrating that the argument as a whole is invalid. It seems pretty clear to me that exposing the flawed logic that an argument is based on both addresses the argument and refutes said argument.

However, it has recently come to my attention that there are apparently types of "logic" by means of which an argument can not only commit, but also include fallacies as an integral part of its form, which somehow renders it irrefutable. This seems to be especially true of arguments in which the conclusion is assumed in the premises, or where everything but the conclusion one is aiming for is defined out of existence. I probably missed something in the Logic 101 class I took a couple of semesters ago, or in my online research into informal fallacies, but how is begging the question ever a valid form of reasoning?

I suppose my next question would be, is there really a school of logic that ignores or is somehow exempt from these basic rules? Where A + B = A is considered a syllogism? Where one can propose categories that only accomodate a single member? Where a fallacy-riddled argument can be deemed untouchable?

Should I be prepared to revise my entire way of thinking and accept that the following sources don't know what they're talking about?

http://web.cn.edu/kwheeler/fallacies_list.html
http://philosophy.lander.edu/logic/syll_fall.html
http://www.unc.edu/depts/wcweb/handouts/fallacies.html
http://en.wikipedia.org/wiki/List_of_fallacies
http://www.fallacyfiles.org/
No, you are right in the first place. An argument with one logical fallacy is invalid. If the fallacious part of the argument was not integral then it is up to the proposer to reframe it without the superfluous part.

[Kopji]

Of course the problem you have is not that.

You see, since it is a fact that there is a God, any failure of an argument to support that fact must indicate a flaw in the argument rather than question the existence of God.

Hope that's been of help. :D

[RandFan]

It is sufficient to refute the argument and to call in to question the conclusion but one can make an invalid argument and still arrive at a correct conclusion.

However, it has recently come to my attention that there are apparently types of "logic" by means of which an argument can not only commit, but also include fallacies as an integral part of its form, which somehow renders it irrefutable. Anything that is not logically impossible, no matter how improbable, is possible.

Using illogic to construct a logically sound argument sounds like nonsense. I would need an example. I find the notion dubious.

[soikins]

However, it has recently come to my attention that there are apparently types of "logic" by means of which an argument can not only commit, but also include fallacies as an integral part of its form, which somehow renders it irrefutable.

Could you give a reference to where did you learn about this type of "logic"?

[Phaedrus74]

<snip>

However, it has recently come to my attention that there are apparently types of "logic" by means of which an argument can not only commit, but also include fallacies as an integral part of its form, which somehow renders it irrefutable. This seems to be especially true of arguments in which the conclusion is assumed in the premises, or where everything but the conclusion one is aiming for is defined out of existence. I probably missed something in the Logic 101 class I took a couple of semesters ago, or in my online research into informal fallacies, but how is begging the question ever a valid form of reasoning?

I suppose my next question would be, is there really a school of logic that ignores or is somehow exempt from these basic rules? Where A + B = A is considered a syllogism? Where one can propose categories that only accomodate a single member? Where a fallacy-riddled argument can be deemed untouchable?

<snip>


It's been a couple of years since I studied the subject but I am not aware of such logics. And if they do exist they are only of theoretical interest to formal/mathematical logicians.

The only problem that is a "real" problem for logic is that a logical inference that starts from false premises is valid and allows you to draw any conclusion.
For instance: "I am not using the internet therefore God exists" is a valid inference. Meaningless, but valid...

[Beerina]

Of course the problem you have is not that.

You see, since it is a fact that there is a God, any failure of an argument to support that fact must indicate a flaw in the argument rather than question the existence of God.

Hope that's been of help. :D


Well, it's kind of hard to prove a god doesn't exist when he has these properties:

1. Infinitely and all-powerful; knows everything.
2. Wants to hide from you.


Of course, zero gods also has that property, as do many gods, and some unicorns and even Santa, I hear.

[Theophage]

Let's not confuse "valid" and "sound" Phaedrus. Yes, your example was a valid construction, but only valid arguments who also have true premises are sound. And only sound arguments prove anything to be true.

[Phaedrus74]

Let's not confuse "valid" and "sound" Phaedrus. Yes, your example was a valid construction, but only valid arguments who also have true premises are sound. And only sound arguments prove anything to be true.

True enough, it was merely to illustrate a point that logic alone doesn't always help. (Must admit that this is a pet peeve I have with logic, not so much with inference as with the interpretation of the logical implication under binary truthvalues in "standard" logic. That one never sat quite right with me.)

Semantics! That's where it's at...
[Oh sorry, is my bias showing ;)]

[slingblade]

Oh, groan, not Semantics. Worst party game ever invented. I'd rather play Pictionary than Semantics.

[Radrook]

It all depends on the importance of the fallacy to the argument.

Here's a website that does a lot of deadly fallacy pointing.
http://www.ridgecrest.ca.us/~do_while/sage/topics.htm

[westprog]

It all depends on the importance of the fallacy to the argument.

Here's a website that does a lot of deadly fallacy pointing.
http://www.ridgecrest.ca.us/~do_while/sage/topics.htm

That's an excellent site to visit if you want to see examples of fallacious logic.

[Mashuna]

Oh, groan, not Semantics. Worst party game ever invented. I'd rather play Pictionary than Semantics.

Last time I played Pictionary, I had to draw Semantics for my team. Well, I say draw, I guess technically it was a sketch, but. . .







Nooooooooo, I've been drawn in. . .

[Silentknight]

It is sufficient to refute the argument and to call in to question the conclusion but one can make an invalid argument and still arrive at a correct conclusion.

Anything that is not logically impossible, no matter how improbable, is possible.

Using illogic to construct a logically sound argument sounds like nonsense. I would need an example. I find the notion dubious.

More to the point, I was recently told by Relic that even though I kept naming fallacies (which I found in his arguments) his argument remained sound, unchallenged, untouched, etc. According to him, demonstrating logical fallacies was not sufficient to invalidate the argument. Mind you, I didn't want anyone else to have to get involved, even though I did point out that his bovine excrement was hardly worth the forum space it was written on. But this is just one small example of an even broader mindset, since it's not the first time I've had someone change the definition of logic or reason on me.

Regardless, I would still like to hear a good case for or against fallacy logic. For those who point out logical fallacies as a debate tactic, why exactly does it work, and how can one defend its use to someone who has no understanding of it? For those who think that fallacies have no relevance to an argument's validity, why not?

[slingblade]

Last time I played Pictionary, I had to draw Semantics for my team. Well, I say draw, I guess technically it was a sketch, but. . .







Nooooooooo, I've been drawn in. . .

Semantics is the gateway trope to punning. You kids and your fads.

[Ron_Tomkins]

A fallacy as you all know is defined as a component of an argument which, being demonstrably flawed in its logic or form, renders the argument invalid in whole, or as an argument using false or invalid inference. One of the more common debate tactics around here is to point out the logical fallacies in an argument being presented, as a means of demonstrating that the argument as a whole is invalid. It seems pretty clear to me that exposing the flawed logic that an argument is based on both addresses the argument and refutes said argument.

However, it has recently come to my attention that there are apparently types of "logic" by means of which an argument can not only commit, but also include fallacies as an integral part of its form, which somehow renders it irrefutable. This seems to be especially true of arguments in which the conclusion is assumed in the premises, or where everything but the conclusion one is aiming for is defined out of existence. I probably missed something in the Logic 101 class I took a couple of semesters ago, or in my online research into informal fallacies, but how is begging the question ever a valid form of reasoning?

I suppose my next question would be, is there really a school of logic that ignores or is somehow exempt from these basic rules? Where A + B = A is considered a syllogism? Where one can propose categories that only accomodate a single member? Where a fallacy-riddled argument can be deemed untouchable?

Should I be prepared to revise my entire way of thinking and accept that the following sources don't know what they're talking about?

http://web.cn.edu/kwheeler/fallacies_list.html
http://philosophy.lander.edu/logic/syll_fall.html
http://www.unc.edu/depts/wcweb/handouts/fallacies.html
http://en.wikipedia.org/wiki/List_of_fallacies
http://www.fallacyfiles.org/

Existential fallacy :D

[Mobyseven]

It's been a couple of years since I studied the subject but I am not aware of such logics. And if they do exist they are only of theoretical interest to formal/mathematical logicians.

I haven't heard about or studied anything that would fit the description given, but I can think of some weird logics that exist - LP is a trivalent logic that is not truth preserving, but instead truth or uncertainty preserving (so out of the values {0, i, 1} an argument is valid iff when the premises are i or 1 the conclusion is i or 1. A weird outcome of this logic is that modus ponens fails...quite frankly, it's not a logic that's particularly good for anything at all (it 'solves' the sorites paradox, but only because modus ponens fails - kind of like swatting a fly with a small meteor).

I suppose that it might be possible to devise a logic whereby some of the formal logical fallacies for classical logic (such as affirming the consequent) could be valid argument forms, but I'm not entirely sure how to tweak the logic to allow for that (or if it can even be done). Moreover, such a logic would be little more than a curiousity, and would be unlikely to correspond to the real world in any way.

[Phaedrus74]

I haven't heard about or studied anything that would fit the description given, but I can think of some weird logics that exist - LP is a trivalent logic that is not truth preserving, but instead truth or uncertainty preserving (so out of the values {0, i, 1} an argument is valid iff when the premises are i or 1 the conclusion is i or 1. A weird outcome of this logic is that modus ponens fails...quite frankly, it's not a logic that's particularly good for anything at all (it 'solves' the sorites paradox, but only because modus ponens fails - kind of like swatting a fly with a small meteor).

I suppose that it might be possible to devise a logic whereby some of the formal logical fallacies for classical logic (such as affirming the consequent) could be valid argument forms, but I'm not entirely sure how to tweak the logic to allow for that (or if it can even be done). Moreover, such a logic would be little more than a curiousity, and would be unlikely to correspond to the real world in any way.

You are probably right about those exotic logics. But something is nagging me and it is the fact that (if I'm not mistaken) Non-Euclidian geometry came about in attempt to prove that Euclidian Geometry was the only consistent/complete (?) geometry.

In other words as crazy as these exotic logics seem, you never know what kind of computers will be designed using them in a couple of decades ;)

[Phaedrus74]

Oh, groan, not Semantics. Worst party game ever invented. I'd rather play Pictionary than Semantics.

Ever spend time studying formal semantics?

Logic without an ontology (and therefore a semantics) is rather impotent in practice.

[slingblade]

Ever spend time studying formal semantics?

Logic without an ontology (and therefore a semantics) is rather impotent in practice.

1. Yes, actually.

2. I know.

3. I've also studied humor.

[Silentknight]

I haven't heard about or studied anything that would fit the description given, but I can think of some weird logics that exist - LP is a trivalent logic that is not truth preserving, but instead truth or uncertainty preserving (so out of the values {0, i, 1} an argument is valid iff when the premises are i or 1 the conclusion is i or 1. A weird outcome of this logic is that modus ponens fails...quite frankly, it's not a logic that's particularly good for anything at all (it 'solves' the sorites paradox, but only because modus ponens fails - kind of like swatting a fly with a small meteor).

I suppose that it might be possible to devise a logic whereby some of the formal logical fallacies for classical logic (such as affirming the consequent) could be valid argument forms, but I'm not entirely sure how to tweak the logic to allow for that (or if it can even be done). Moreover, such a logic would be little more than a curiousity, and would be unlikely to correspond to the real world in any way.

Well, thanks for playing devil's advocate anyway. I was more interested in the former of my two questions in my last post, which was how to explain basic logic to someone who is operating off his personal definition of logic, and thus committing fallacies left and right. Seriously, it's bad enough when you're forced to start a debate defending the use of logic and reason, but what do you do if someone has his own crazy idea of what those words mean?

Incidentally, I hope the mild sarcasm in the OP wasn't too obscure, since I had just gotten flamed by some apologist who did just that, claiming that my pointing out of fallacies doesn't make his arguments invalid or illogical. However the question as to whether it's sufficient in a debate to demonstrate logical fallacies in order to refute an argument was serious. I know that an argument can have a flawed construction and still come to a correct conclusion, but that was beside the point.

[balrog666]

Well, thanks for playing devil's advocate anyway. I was more interested in the former of my two questions in my last post, which was how to explain basic logic to someone who is operating off his personal definition of logic, and thus committing fallacies left and right. Seriously, it's bad enough when you're forced to start a debate defending the use of logic and reason, but what do you do if someone has his own crazy idea of what those words mean?

Incidentally, I hope the mild sarcasm in the OP wasn't too obscure, since I had just gotten flamed by some apologist who did just that, claiming that my pointing out of fallacies doesn't make his arguments invalid or illogical. However the question as to whether it's sufficient in a debate to demonstrate logical fallacies in order to refute an argument was serious. I know that an argument can have a flawed construction and still come to a correct conclusion, but that was beside the point.


Demonstrating logical fallacies in an argument doesn't refute the argument but it does invalidate it.

If they haven't made a valid argument in the first place, there is nothing to "refute".

[Kevin_Lowe]

Well, thanks for playing devil's advocate anyway. I was more interested in the former of my two questions in my last post, which was how to explain basic logic to someone who is operating off his personal definition of logic, and thus committing fallacies left and right. Seriously, it's bad enough when you're forced to start a debate defending the use of logic and reason, but what do you do if someone has his own crazy idea of what those words mean?

I've never succeeded in that project. Trying to explain reason to an unreasonable person who thinks they are reasonable is like trying to levitate by pulling on your shoelaces.

Once someone demonstrates that they can't or won't let go of their fallacies (I've run into a few people who refuse to let go of the naturalistic fallacy, that everything natural is morally good) there's no basis for a reasonable conversation.

[Mobyseven]

You are probably right about those exotic logics. But something is nagging me and it is the fact that (if I'm not mistaken) Non-Euclidian geometry came about in attempt to prove that Euclidian Geometry was the only consistent/complete (?) geometry.

In other words as crazy as these exotic logics seem, you never know what kind of computers will be designed using them in a couple of decades ;)

Heh. We already have some of those - there are paraconsistent logics that could, in theory, have practical applications in computing - for a very basic example, a computer (or really, a specific programming language) operating on classical logic could receive instructions that a particular piece of information is both true and false, and to assign it both a 0 and 1 value; if it is operating on a basic paraconsistent logic then rather than assigning both 0 and 1 to the piece of information, it is related to two other pieces of information called 'true' and 'false' that can both take either the value 0 or 1.

Well, thanks for playing devil's advocate anyway. I was more interested in the former of my two questions in my last post, which was how to explain basic logic to someone who is operating off his personal definition of logic, and thus committing fallacies left and right. Seriously, it's bad enough when you're forced to start a debate defending the use of logic and reason, but what do you do if someone has his own crazy idea of what those words mean?

Grab a drink and relax. Not worth stressing over 99% of the time.

Demonstrating logical fallacies in an argument doesn't refute the argument but it does invalidate it.

Well, it does refute the argument. What it doesn't refute is the conclusion.

[Phaedrus74]

1. Yes, actually.

2. I know.

3. I've also studied humor.

In that case, excuse me while I go and brush the chip off my shoulder :boxedin:

[slingblade]

In that case, excuse me while I go and brush the chip off my shoulder :boxedin:

Nah, don't do that. Someone will just trip over it. :p


No harm, no foul; carry on, sweetie.

[RandFan]

Regardless, I would still like to hear a good case for or against fallacy logic. For those who point out logical fallacies as a debate tactic, why exactly does it work, and how can one defend its use to someone who has no understanding of it? For those who think that fallacies have no relevance to an argument's validity, why not? "Fallacy logic"? I don't know what that is but I think I have an idea. I think your term is an oxymoron. And while it can be seen as a "tactic" that really isn't the purpose.

Bob: I have three puppies.
Jill: No you don't. You have two.
Bob: 1+1=3
Jill: No it doesn't. 1+1=2

That's it. That's really all you need to know. The universe only works in a logical way. There is nothing illogical in the natual world. We can think abstractly and we can construct illogical statements but that's it. Sometimes, like Bob in the example above, we make statements that are not logical. The point of identifying fallacy is to simply demonstrate to the person making the argument that we can't rely on the argument.

Remember what a fallacy is in the first place: A fallacy is a component of an argument which, being demonstrably flawed in its logic or form, renders the argument invalid in whole.

See Logic & Fallacies Constructing a Logical Argument (1997) (http://www.infidels.org/library/modern/mathew/logic.html)

[Silentknight]

I agree, that's a great article. I first read it about 4 years ago and it's one of the things that got me interested in studying logic as it applies to religious or philosophical debate. Unfortunately, listing all the sources in the world isn't going to break through the insulated apologist arrogance that ascribes to its own circular version of logic at the expense of all else.

As the saying goes, you can lead a horse to water, but you can't stop it from defecating into the river while insisting it's doing so to improve the water quality.

[RandFan]

I agree, that's a great article. I first read it about 4 years ago and it's one of the things that got me interested in studying logic as it applies to religious or philosophical debate. Unfortunately, listing all the sources in the world isn't going to break through the insulated apologist arrogance that ascribes to its own circular version of logic at the expense of all else.

As the saying goes, you can lead a horse to water, but you can't stop it from defecating into the river while insisting it's doing so to improve the water quality.If someone truly believes that the moon doesn't exist even after they've seen evidence to the contrary it's unlikely that any argument will convince that person otherwise. Logical argument is of no value to those not committed to adhering to logic. It's like playing a game where one person is free to change the rules when it suits him or her.

I'm an atheist today because I committed myself to accept the truth no matter what, but I gotta be honest, I didn't always accept the truth when I found it. It's not easy to accept the truth when your personality is constructed around a certain world view and the truth conflicts with that view. For many like myself it is at best a long slow process.

Be honest and avoid fallacy yourself. It's the best you can do.

[Radrook]

That's an excellent site to visit if you want to see examples of fallacious logic.

The typical unsubstantiated fanatical reaction. This is the same person who would swallow all the fallacious evolutionist drivel hook line and sinker as long as it has thew evo tag on it.

[RandFan]

...the fallacious evolutionist drivel...What?

Why I left Young-earth Creationism (http://www.richarddawkins.net/article,3198,Why-I-left-Young-earth-Creationism,Glenn-R-Morton)

But eventually, by 1994 I was through with young-earth creationISM. Nothing that young-earth creationists had taught me about geology turned out to be true. I took a poll of my ICR graduate friends who have worked in the oil industry. I asked them one question.

"From your oil industry experience, did any fact that you were taught at ICR, which challenged current geological thinking, turn out in the long run to be true? ,"

That is a very simple question. One man, Steve Robertson, who worked for Shell grew real silent on the phone, sighed and softly said 'No!' A very close friend that I had hired at Arco, after hearing the question, exclaimed, "Wait a minute. There has to be one!" But he could not name one. I can not name one. No one else could either. One man I could not reach, to ask that question, had a crisis of faith about two years after coming into the oil industry. I do not know what his spiritual state is now but he was in bad shape the last time I talked to him.
The evidence is just too great. There have been prediction after prediction made by evolutionary scientists that have turned out to be true. Evolution is a science that is being used right now to solve real world problems (like finding oil and developing medicine). So called creation science isn't used in any discipline to solve any problems because it's wrong but most importantly, it's not science.

You could more easily deny the existence of the moon. There is far more evidence for evolution. It is an indisputable fact.

[slingblade]

The typical unsubstantiated fanatical reaction. This is the same person who would swallow all the fallacious evolutionist drivel hook line and sinker as long as it has thew evo tag on it.

Welcome to Fallacyland! Above, you see a prime example of Argumentum ad Hominem. Please stay with the tour, and keep all brain cells firmly in an attentive and skeptical position. Thank you.

[Phaedrus74]

Heh. We already have some of those - there are paraconsistent logics that could, in theory, have practical applications in computing - for a very basic example, a computer (or really, a specific programming language) operating on classical logic could receive instructions that a particular piece of information is both true and false, and to assign it both a 0 and 1 value; if it is operating on a basic paraconsistent logic then rather than assigning both 0 and 1 to the piece of information, it is related to two other pieces of information called 'true' and 'false' that can both take either the value 0 or 1.


(I hope SilentKnight doesn't mind if I continue off-topic for a second...)

Paraphrasing:

What happens is that an extra epistemic layer is built in (I'm just trying to recast your description using concepts I am more familiar with).

The "true" and "false" that are referenced could be seen as shorthand for "Is believed to be true/false" these two beliefs being obviously candidates for being true or false (1 or 0) themselves. Sort of deferred truth assignment....

I'll stop now but the image that springs to mind is a type of branching update-semantics that one of my profs (Veltman) used to be (is still?) working on.

Back to the topic...

SilentKnight, pointing out logical fallacies to defuse an argument can be useful to gain the upper hand in a debate.

If you seriously want to change the mind of the other person its success hinges crucially on the willingness of the other person to have their mind changed. (It is (probably) a very effective way for testing this willingness and consequently for determining whether your energy might be better spent elsewhere...)

[TMiguel]

Just because some one use a fallacy in order to try to support a point, it is not necessarily true that the point is also false. The truth does not depend on the ignorance of the person trying to prove it.
Although you can dismiss some conclusions that one has made, if the logic used was a fallacy and therefore he could not have reached to such conclusion (and so other dismissed possibilities are still open, and such conclusion no more valid then any other possibility).
You can only dismiss a point entirely if it’s implication require it to be false (or the negative of said point true).
Some of you have argued that some points result in paradoxes where statements can not be either true or false, but that is a totally different level.

[westprog]

The typical unsubstantiated fanatical reaction. This is the same person who would swallow all the fallacious evolutionist drivel hook line and sinker as long as it has thew evo tag on it.


The reason that Creationism is incompatible with Christianity is that it relies, fundamentally, on untruths. The arguments of the creationists are dishonest.

That is not to say that all creationists are liars. But the arguments that they use are, invariably, dishonest arguments, and the result in many cases - as we see here - is that the acceptance of the reality of evolution goes hand in hand with a rejection of religious faith.

[fls]

A fallacy as you all know is defined as a component of an argument which, being demonstrably flawed in its logic or form, renders the argument invalid in whole, or as an argument using false or invalid inference. One of the more common debate tactics around here is to point out the logical fallacies in an argument being presented, as a means of demonstrating that the argument as a whole is invalid. It seems pretty clear to me that exposing the flawed logic that an argument is based on both addresses the argument and refutes said argument.

However, it has recently come to my attention that there are apparently types of "logic" by means of which an argument can not only commit, but also include fallacies as an integral part of its form, which somehow renders it irrefutable. This seems to be especially true of arguments in which the conclusion is assumed in the premises, or where everything but the conclusion one is aiming for is defined out of existence. I probably missed something in the Logic 101 class I took a couple of semesters ago, or in my online research into informal fallacies, but how is begging the question ever a valid form of reasoning?

I suppose my next question would be, is there really a school of logic that ignores or is somehow exempt from these basic rules? Where A + B = A is considered a syllogism? Where one can propose categories that only accomodate a single member? Where a fallacy-riddled argument can be deemed untouchable?

Should I be prepared to revise my entire way of thinking and accept that the following sources don't know what they're talking about?

http://web.cn.edu/kwheeler/fallacies_list.html
http://philosophy.lander.edu/logic/syll_fall.html
http://www.unc.edu/depts/wcweb/handouts/fallacies.html
http://en.wikipedia.org/wiki/List_of_fallacies
http://www.fallacyfiles.org/

Without going to the trouble of trying to figure out which discussion you are referring to...

I suspect that what you are being told is that invalidating one argument in support of a particular conclusion does not mean that no valid arguments exist for that conclusion. That is, even though you may have refuted my specific argument, since I know the conclusion to be true, there must exist a valid argument out there, somewhere. If I stumble around a bit, I may trip over it.

Linda

[Dragoonster]

I'm really regretting not taking logic in college, maybe there's a local community course. As is my only knowledge of it is through osmosis here and in prior forums. Mind if I ask a few general questions?

Is Aristotlean logic still used in philosophy arguments?
Is Boolean logic preferred?
Is predicate logic preferred? (that one scares me with all the math :( )

Are there genres of each--formal, linguistic, mathematical, etc? Am I right in that the type primarily used here is linguistic, based on or translated from Boolean?

Which of these use Venn diagrams?

as for the OP, looking through the links I'm not sure I understand the Existential Fallacy. There were a lot of examples of Unicorns and Martians, but also ones of accepted sets (I think), so I'm not sure if the flaw is that the sets aren't accepted as existing, or if it's that the conclusion is "some" rather than "all"?

If the latter, is it correct that this is because universal predicates or postulates can't lead to a particular (some, instead of all or none [?]) position? Also, is it understood that in saying "some" that means that "some [at least one] not"? Or can "some" be "all"?

If the former, I don't see how this is practical, as every set could be disputed, or every argument would have to establish the set exists through prior logic, regressing back and back. For instance, "all Swedes are blond" would have to rely on accepting (or proving earlier) that there are Swedes and blonds.

Thanks.

[slingblade]

I'm really regretting not taking logic in college, maybe there's a local community course. As is my only knowledge of it is through osmosis here and in prior forums. Mind if I ask a few general questions?

Is Aristotlean logic still used in philosophy arguments?
Is Boolean logic preferred?
Is predicate logic preferred? (that one scares me with all the math :( )

Are there genres of each--formal, linguistic, mathematical, etc? Am I right in that the type primarily used here is linguistic, based on or translated from Boolean?

Which of these use Venn diagrams?

as for the OP, looking through the links I'm not sure I understand the Existential Fallacy. There were a lot of examples of Unicorns and Martians, but also ones of accepted sets (I think), so I'm not sure if the flaw is that the sets aren't accepted as existing, or if it's that the conclusion is "some" rather than "all"?

If the latter, is it correct that this is because universal predicates or postulates can't lead to a particular (some, instead of all or none [?]) position? Also, is it understood that in saying "some" that means that "some [at least one] not"? Or can "some" be "all"?

If the former, I don't see how this is practical, as every set could be disputed, or every argument would have to establish the set exists through prior logic, regressing back and back. For instance, "all Swedes are blond" would have to rely on accepting (or proving earlier) that there are Swedes and blonds.

Thanks.

I really want to answer all this, but I fear making mistakes or not saying it properly and looking stupid. :)

[Silentknight]

(I hope SilentKnight doesn't mind if I continue off-topic for a second...)

Paraphrasing:

What happens is that an extra epistemic layer is built in (I'm just trying to recast your description using concepts I am more familiar with).

The "true" and "false" that are referenced could be seen as shorthand for "Is believed to be true/false" these two beliefs being obviously candidates for being true or false (1 or 0) themselves. Sort of deferred truth assignment....

I'll stop now but the image that springs to mind is a type of branching update-semantics that one of my profs (Veltman) used to be (is still?) working on.
I don't mind. It's relevant to the topic, and I find it interesting, even if I don't fully understand it. I just haven't taken the course that covers that type of material yet, and I haven't encountered it in my independent studies. :)

Back to the topic...

SilentKnight, pointing out logical fallacies to defuse an argument can be useful to gain the upper hand in a debate.

If you seriously want to change the mind of the other person its success hinges crucially on the willingness of the other person to have their mind changed. (It is (probably) a very effective way for testing this willingness and consequently for determining whether your energy might be better spent elsewhere...)
The problem wasn't so much changing someone's mind as it was dealing with a personal definition of logic that had nothing to do with any of the rules or structure I was familiar with, or that are commonly accepted.

[Robin]

It all depends on the importance of the fallacy to the argument.
No. If an argument contains superfluous detail then it is the responsibility of the proposer to reframe the argument without the superfluity, not of the reader to decide what is important and what is not.

[RandFan]

Is Aristotlean logic still used in philosophy arguments?
Is Boolean logic preferred?
Is predicate logic preferred? (that one scares me with all the math :( )I wish I were more competent. I can only offer my understanding and hopefully someone more qualified than myself can add or correct me. It's been two decades since I took logic at the university and I've demonstrated on more than one occasion that I don't always have the best grasp of the subject I love so much and act more authoritatively than I have right to. In other words, I've made mistakes.

It's a fun and fascinating and often esoteric and mind numbing field or, fields. As you already intimate there are many types of logic. Formal and informal, deductive and inductive, prepositional, propositional, symbolic, mathematical, etc.

First, to quote the Infidels treatise, "logical reasoning is not an absolute law that governs the universe".

Second, one form of logic isn't better than another without some context to make a judgment. Asking which logic is preferred is like asking which tool is preferred between a hammer or screwdriver? It depends on the problem you are trying to solve.

Finally, Aristotelian logic is absolutely still used in philosophy and science though it isn't always referred to as Aristotelian logic but most logical systems today owe their foundations to Aristotelian logic (see syllogisms and dialectics).

Are there genres of each--formal, linguistic, mathematical, etc? There is some ambiguity in the terms. Formal logic often means symbolic or mathematical logic however formal logic can be both language based and symbolic (mathematical).

All humans are mortal.
Socrates is a human.
Therefore Socrates is mortal.

∀ x = y
s = x
s → y

Am I right in that the type primarily used here is linguistic, based on or translated from Boolean?Boolean is dichotomous (1 or 0, on or off) and mathematical (algebraic). Many forms of logic are used daily in this forum but informal logic is the most common but often incorporating other forms. Linguistics is the underlying logic we use to communicate and not necessarily to formulate arguments.

Think of it like a computer. The computer processes data using computer language (assembly language). However the logic employed by the programmer is likely a program like C++ and there is at least one language between the two that acts as a mediator or translator if you wish.

Which of these use Venn diagrams?No single system of logic system (see set theory (http://en.wikipedia.org/wiki/Set_theory) and categorical logic (http://www.google.com/search?q=categorical+logic&rls=com.microsoft:en-us&ie=UTF-8&oe=UTF-8&startIndex=&startPage=1)).

I'll address the other when I have more time.

[Dragoonster]

Thanks for clearing some things up Rand. :)

I'm glad it doesn't seem I'd need to be a master of the more mathematical structure stuff if I take a class (or, after the class). I was terrible in post-algebra with all the weird symbols and sub-symbols. But loved geometry and the Venn diagrams are much easier for me to grok.

I'm slowly learning the "output" but some of the programming seems daunting (nice analogy)

[slingblade]

Thank you, RandFan. I lacked the confidence to try, and you said it better than I could have, if I had tried. :)

[RandFan]

Thanks for clearing some things up Rand. :)

I'm glad it doesn't seem I'd need to be a master of the more mathematical structure stuff if I take a class (or, after the class). I was terrible in post-algebra with all the weird symbols and sub-symbols. But loved geometry and the Venn diagrams are much easier for me to grok.

I'm slowly learning the "output" but some of the programming seems daunting (nice analogy) Glad to help. I'm thinking of taking a refresher course myself. BTW, there are some posters on this forum who are very good with formal logic. I can't remember user names but there have been a few that have fixed my errors and I couldn't thank them enough. You might want to post on the science and math forum if you have further questions and treat my info as you would wikipedia. I've a fairly good grasp of the subject but I'm not an expert. :)

[my_wan]

However, it has recently come to my attention that there are apparently types of "logic" by means of which an argument can not only commit, but also include fallacies as an integral part of its form, which somehow renders it irrefutable. This seems to be especially true of arguments in which the conclusion is assumed in the premises, or where everything but the conclusion one is aiming for is defined out of existence.

I got into a debate in early April that might qualify here. I've had no formal training in logic. I spot fallacies easy enough but identifying their names are often quiet difficult for me. Anyhow the initial claim was:
Okay, frauds and deluded people. But I do take exception to debunkers that constantly lie by saying that there is no evidence for any of this. Clearly they are more interested in their opinion than any potentially credible evidence, which is a hallmark of a crackpot debunker.
The interesting argument came after shutting down the poster and another tried to come to the rescue with this post:
my_wan,
I have attempted to summarize the argument you are opposing.

1. Anecdotes are a form of evidence.
2. Anecdotes are always or nearly always provided in support of paranormal claims.
3. Some debunkers say there is no evidence for such claims.
Therefore, some debunkers lie.

Are either of the 3 premises invalid?
If so, then the argument is unsound.

Does the conclusion follow logically from the premises?
If not, then the argument is unsound.

What do you think?
I responded with this:
1. makes the logical error of being true by definition yet failing to provide evidence for that which is being claimed. You then specify the evidence as pertaining to claims in 3, a specification not contained in 1.

The logic in 1. requires the law of the excluded middle, i.e., it excludes a third possibility, yet you include the "middle" in 3. when you say "evidence for such claims". "Evidence" and "evidence of X" are not even the same logical category.
The law of the excluded middle is something I am familiar with. It is even related to some interesting physics. Would H8wm4m's argument qualify as one in which the refutation is "defined out of existence"? Is there a category for this particular logical error? In essence he attempted to use a truth value from a boolean statement to establish a boolean truth value of a non-boolean statement.

[Phaedrus74]

I don't mind. It's relevant to the topic, and I find it interesting, even if I don't fully understand it. I just haven't taken the course that covers that type of material yet, and I haven't encountered it in my independent studies. :)


The stuff Moby refers to is pretty rarified, the things I am familiar with are basically extensions of first order predicate logic. For formal semantics this generally suffices. You could check out: The ILLC (http://www.illc.uva.nl/) their publications section is filled to the brim with interesting stuff (though not for the faint of heart!). This paper (http://www.illc.uva.nl/Publications/ResearchReports/PP-2008-42.text.pdf) should be a decent starting point.


The problem wasn't so much changing someone's mind as it was dealing with a personal definition of logic that had nothing to do with any of the rules or structure I was familiar with, or that are commonly accepted.

Sounds to me they were using "logic" in it's everyday sense not as the technical term. But I wasn't a witness to the exchange so, maybe mistaken...