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Logical Fallacies
Posted 3/11/08 , edited 3/11/08
Here is a site that everyone, in my opinion, should read:

http://www.logicalfallacies.info/

The following is an except from the above linked site.

What is a Logical Fallacy?

A logical fallacy is, roughly speaking, an error of reasoning. When someone adopts a position, or tries to persuade someone else to adopt a position, based on a bad piece of reasoning, they commit a fallacy. I say “roughly speaking” because this definition has a few problems, the most important of which are outlined below. Some logical fallacies are more common than others, and so have been named and defined. When people speak of logical fallacies they often mean to refer to this collection of well-known errors of reasoning, rather than to fallacies in the broader, more technical sense given above.

Formal Fallacies (Deductive Fallacies)

Philosophers distinguish between two types of argument: deductive and inductive. For each type of argument, there is a different understanding of what counts as a fallacy.

Deductive arguments are supposed to be water-tight. For a deductive argument to be a good one (to be “valid”) it must be absolutely impossible for both its premises to be true and its conclusion to be false. With a good deductive argument, that simply cannot happen; the truth of the premises entails the truth of the conclusion.

The classic example of a deductively valid argument is:

(1) All men are mortal.
(2) Socrates is a man.
Therefore:
(3) Socrates is mortal.

It is simply not possible that both (1) and (2) are true and (3) is false, so this argument is deductively valid.

Any deductive argument that fails to meet this (very high) standard commits a logical error, and so, technically, is fallacious. This includes many arguments that we would usually accept as good arguments, arguments that make their conclusions highly probable, but not certain. Arguments of this kind, arguments that aren’t deductively valid, are said to commit a “formal fallacy”.

Informal Fallacies

Inductive arguments needn’t be as rigorous as deductive arguments in order to be good arguments. Good inductive arguments lend support to their conclusions, but even if their premises are true then that doesn’t establish with 100% certainty that their conclusions are true. Even a good inductive argument with true premises might have a false conclusion; that the argument is a good one and that its premises are true only establishes that its conclusion is probably true.

All inductive arguments, even good ones, are therefore deductively invalid, and so “fallacious” in the strictest sense. The premises of an inductive argument do not, and are not intended to, entail the truth of the argument’s conclusion, and so even the best inductive argument falls short of deductive validity.

Because all inductive arguments are technically invalid, different terminology is needed to distinguish good and bad inductive arguments than is used to distinguish good and bad deductive arguments (else every inductive argument would be given the bad label: “invalid”). The terms most often used to distinguish good and bad inductive arguments are “strong” and “weak”.

An example of a strong inductive argument would be:

(1) Every day to date the law of gravity has held.
Therefore:
(2) The law of gravity will hold tomorrow.

Arguments that fail to meet the standards required of inductive arguments commit fallacies in addition to formal fallacies. It is these “informal fallacies” that are most often described by guides to good thinking, and that are the primary concern of most critical thinking courses and of this site.
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Posted 3/11/08
Does this thread have a purpose? I understand that reasoning isn't the strongest trait of many users who go here, but this board is for discussion threads. Where is the discussion?
Posted 3/11/08
This thread pertains to discussion, though there isn't too much to discuss about the subject itself. People could perhaps add additional fallacies that they've heard of or encountered.
Posted 3/11/08
The sticker should be granted, but I don't really....know how to discuss about this matter...D:

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Posted 3/11/08
Hmm I vote for sticky too but I dont know about the other mods >_>


ok how about if you also add what inductive and deductive reasoning is, and all that jazz. Argument guidelines basically...to make it more of a sticky worthy
Posted 3/11/08

mauz15 wrote:
ok how about if you also add what inductive and deductive reasoning is, and all that jazz. Argument guidelines basically...to make it more of a sticky worthy

Ok, will do.
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Posted 3/17/08
we are learning this in Religious Studies at school. thanks for the revision
Posted 3/17/08
i think it would be a good idea if we could post (quote) some logical fallacies committed by CR forum users. then we'll discuss it here. it would be educational and you know, we can teach each other the art of reasoning. (analytical)

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Posted 3/17/08
ive decided im going to ask an actual question today:

what is there to discuss in this? the sky is blue...thanks for the heads up
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Posted 3/27/08

shibole wrote:

The classic example of a deductively valid argument is:

(1) All men are mortal.
(2) Socrates is a man.
Therefore:
(3) Socrates is mortal.

It is simply not possible that both (1) and (2) are true and (3) is false, so this argument is deductively valid.

Any deductive argument that fails to meet this (very high) standard commits a logical error, and so, technically, is fallacious. This includes many arguments that we would usually accept as good arguments, arguments that make their conclusions highly probable, but not certain. Arguments of this kind, arguments that aren’t deductively valid, are said to commit a “formal fallacy”.



I've got a question:

You said that argument is valid, Right?
An argument is valid just in case that it is impossible to have an instance of true premises and false conclusion. If an argument has a form that allows an instance of true premises and false conclusion, then it is invalid. Right?

Consider this argument. Is it valid?

Reading is Knowledge. (T)
Knowledge is Power. (T)
Power is Corruption. (T)
Corruption is a Crime. (T)
Crime does not pay. (T)
----------------------------------------------------------
Therfore, reading will make you go broke. (F)

This argument form is the same as yours. It allows an instance of true premises and false conclusion, so is it valid.
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Posted 3/27/08
Simply declareing "A is B" doesn't necesarily make it True nor Valid.
Clear and precise definition of A and B, as well as the criteria or basis of the evaluation/equation are needed.

In the case of "All men are mortal", it can be interperted as "All human beings will meet physical death" and it's a widely accepted evaluation (although debatable).

However, "Reading is Knowledge" is way too vague.
You can't say any kind of reading will always bring you Knowledge.
It's like declaring "Eating is Fat" It's nearly absurd.

In other words, the validity of premises is very important in any logical and/or constructive discussion.

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Posted 3/27/08

qweruiop wrote:

Consider this argument. Is it valid?

Reading is Knowledge. (T)
Knowledge is Power. (T)
Power is Corruption. (T)
Corruption is a Crime. (T)
Crime does not pay. (T)
----------------------------------------------------------
Therfore, reading will make you go broke. (F)

This argument form is the same as yours. It allows an instance of true premises and false conclusion, so is it valid.


Though you're right on the grounds that all of these statements have valid meanings, they don't necessarily work as a syllogism. When you say "power is corruption," you don't really mean it as an absolute equality. "Power often leads to corruption" is probably a more accurate interpretation.

Reading can give one higher knowledge. - (T)
Knowledge used correctly can lead to power. - (T)
Power is likely to corrupt. - (T)
Corruption isn't a crime in itself, but it may lead to crimes. - (T)

Therefore, reading may lead to crime. (T)

That conclusion is valid. Yours, though technically all of the statements hold true, they are taken too absolutely to make an accurate conclusion. In truth, the syllogism you provided was actually flawed. Reading does not really equal knowledge. The statement reading is knowledge is only based on a likelihood/purpose. All of the statements are probabilities, so the conclusion must also hold probability. Otherwise, the syllogism comes to a growing error.
Posted 3/27/08

qweruiop wrote:
You said that argument is valid, Right?

I didn't say it, I just copied and pasted from the linked web site. But yes, I'd concur with the author of the web site that the argument that you refer to is valid.
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Posted 3/27/08

gwgw wrote:

Simply declareing "A is B" doesn't necesarily make it True nor Valid.
Clear and precise definition of A and B, as well as the criteria or basis of the evaluation/equation are needed.

In the case of "All men are mortal", it can be interperted as "All human beings will meet physical death" and it's a widely accepted evaluation (although debatable).

However, "Reading is Knowledge" is way too vague.
You can't say any kind of reading will always bring you Knowledge.
It's like declaring "Eating is Fat" It's nearly absurd.

In other words, the validity of premises is very important in any logical and/or constructive discussion.



See below.


winsomemastix wrote:


qweruiop wrote:

Consider this argument. Is it valid?

Reading is Knowledge. (T)
Knowledge is Power. (T)
Power is Corruption. (T)
Corruption is a Crime. (T)
Crime does not pay. (T)
----------------------------------------------------------
Therfore, reading will make you go broke. (F)

This argument form is the same as yours. It allows an instance of true premises and false conclusion, so is it valid.


Though you're right on the grounds that all of these statements have valid meanings, they don't necessarily work as a syllogism. When you say "power is corruption," you don't really mean it as an absolute equality. "Power often leads to corruption" is probably a more accurate interpretation.

Reading can give one higher knowledge. - (T)
Knowledge used correctly can lead to power. - (T)
Power is likely to corrupt. - (T)
Corruption isn't a crime in itself, but it may lead to crimes. - (T)

Therefore, reading may lead to crime. (T)

That conclusion is valid. Yours, though technically all of the statements hold true, they are taken too absolutely to make an accurate conclusion. In truth, the syllogism you provided was actually flawed. Reading does not really equal knowledge. The statement reading is knowledge is only based on a likelihood/purpose. All of the statements are probabilities, so the conclusion must also hold probability. Otherwise, the syllogism comes to a growing error.


Hmm....you're right.
Alright. I see they are not exactly equivalents. So I shouldn't really use the word "is"
But what if we change the form of this argument into a hypothetical syllogism?

If one reads, then he will gain knowledge. (T)
If one gains knowledge, then he will gain power. (T)
If one gains power, then he will become corrupt. (T)
If one becomes corrupt, then he will commit crimes. (T)
If one commits crimes, then he will not earn money (lawfully). (T)
------------------------------------------------------------------------------
Therefore, if one reads, then he will not earn money (lawfully). (F)


Support for premise 1: If one reads, he will at least gain knowledge of the fact that he read something.
Support for premise 2: Knowledge empowers your mind.
Support for premise 3: Power corrupts. Absolute power corrupts absolutely.
Support for premise 4: The definition of corruption from the Websters dictionary: inducement to wrong by improper or unlawful means (as bribery). Unlawful=crime.
Support for premise 5: The keyword is "earn lawfully."
Counterexample for the conclusion: There are several legal jobs that pay for reading. For instance, a book critic. He gets paid for reading and critiquing books.

Now is the argument valid or invalid?

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Posted 3/27/08
The problem still remains. This syllogism states absolutes, using the term "will" instead of "may." People who commit crimes can also earn legal money. Similarly, those who read might wind up as criminals, but simultaneously have been reaping many of the good sides of reading and the benefits of knowledge. There are too many errors in logic here.

If one reads, then he will gain knowledge, moral strength, culture, exposure, and *money. (T)
If one gains knowledge, then he will gain power, **money, and wisdom. (T)
If one gains power, then he will become corrupt. But wisdom and moral strength can counteract this.(T)
If one becomes corrupt, then he will commit crimes. (T) [No error]
If one commits crimes, then he will not earn money (lawfully). (T) <= Wrong. Counter: I watched licensed Japanese media. This is a crime. I have a legal monthly salary.
------------------------------------------------------------------------------
Therefore, if one reads, then he will not earn money (lawfully). (F)

Support for premise 1: See your counterexample for money, in addition to the moral content and culture in reading that would be gained.
Support for premise 2: Knowledge is valuable. Knowledge is money. College graduates earn more than high school graduates.
Support for premise 3: Morality is the opposing force to corruption
Support for premise 4: N/A
Support for premise 5: See example above.

I could go on. The point however, is that you shouldn't be so hasty to question the method. More likely than not, if A=B=C, but A /= C., then A = B or B = C is false. If A=B=C were true, then there is no way that A could not equal C.
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