Talk:Informal fallacy

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Revision of article in view of expansion

I have revised this to improve accuracy (as discussed professionally in logic texts, etc.) and to help align and coordinate it with other Wiki articles on logic, fallacies, etc. I have a partial draft to expand this article, and hope to post it over the next several days.jbessie 21:45, 13 April 2007 (UTC)

Hi Joseph,

The text you added to the page Informal fallacy does not conform to the WP style guide. Your text reads:

"In general, the term fallacy refers to a mistake in reasoning--usually one that is not obvious on first appearance. In the study of logic, fallacies are generally devided between formal and informal. In the former type, the error in reasoning can be attributed to a structural element in the reasoning, typically it's logical form. Informal fallacies, by contrast, cannot be identified or characterized in this way. Rather, these are errors in reasoning that have to do with broader issues of rational inference than can be represented formally."

The word you bolded was 'fallacy' and not 'informal fallacy', which is the subject of the article. The opening line should be about the article's subject informal fallacy and the first paragraph should not discuss what a 'fallacy' is in general. Although perhaps the last couple of sentences could summarise the difference between between informal and formal fallacies.

Your new introduction belongs on the page fallacy, not here. That said the article is in need of expansion and an understandable introduction, which it didn't have before. I think that some of the key points to note with the article are that: 1. Informal fallacies are valid (but most often unsound) when the assumptions (hidden co-premises) are stated and invalid when they are not stated (as most often occurs). They are valid forms of reasonsing but flawed due to a false premise. You put this as :"(informal fallacies) are errors in reasoning that have to do with broader issues of rational inference than can be represented formally." - this sentence is is vague and hard to understand. It is also wrong, as informal fallacies can be represented formally. For instance here, here and here. -- Grumpyyoungman01 06:49, 14 April 2007 (UTC)

Grumpyyoungman,

There is a sense in which what you say is correct regarding informal fallacies, viz., that they are invalid if left unexplicated, but valid when unstated premises are added. This approach to the general topic of informal fallacies, however, would seem to lay stress only on deductive arguments--but plenty of discussion of informal fallacies has to do with inductive arguments, where the question of validity never arises (rather, the usual expression is something like "inductive strength"--some examples are Hasty Generalization, Appeal to Authority, False Cause, Weak Analogy). Take Hasty Generalization:

s is a P and s is a Q

therefore, All P's are Q's

One could add a premise, say,

For any x and for any Φ, if x is P and x is Φ, then all P's are Φ,

which would make the argument deductively valid--and of course the premise in question is likely to be false (depending on what the particulars are in the case in question), but this approach tends to obliterate the distinction between induction and deduction. It is important to distinguish between a principle of reasoning (deductive or inductive, on the one hand) from premises of an argument, on the other.

Also, the expression "co-premise" appears to be one allied with the language of arugment maps, etc., and some attempt might be made to connect this subject to the traditional study of logic. A very popular logic and critical thinking text--Patrick Hurley's A Concise Introduction to Logic--uses neither expression (at least, the last time I looked, which was some while ago!). It might also be useful to connect the discussion to an article on formal fallacies, on which there is also some history and overlap with natural language (e.g., the Fallacy of Four Terms, Affirming the Consequent, Denying the Antecedent, etc.). Although the argument map illustration may be useful, it might better be introduced as one of several techniques for diagramming arguments, and the argument in its original form presented first and then (by way of illustration) more fully explicated by the map.

It is also noteworthy that there are in fact sound arguments that we should nevertheless reject (note, by the way, that use of 'sound' and 'unsound' also connotes a deductive context). Suppose it is true that nothing can be accelerated past the speed of light. Still, the following argument should be rejected as failing to achieve its aim:

Nothing can go faster than light.

Therefore, nothing can go faster than light.

Even though it's deductively valid and has a true premise, one ought not to be convinced by it. If the purpose of the argument is to demonstrate the truth of an otherwise unaccepted claim on the basis of other claims already known or believed, this argument fails to give rational grounds for accepting its conclusion. (One way to characterise Petitio Principii--Begging the Question--that I like is this: An argument begs the question when its premises could not all be accepted unless one already accepted the conclusion.)--jbessie 15:46, 17 April 2007 (UTC)

Hi Joseph,

You are right regarding the validity and invalidity of informal arguments in deductive and inductive form. I will edit the page to reflect this.

Although the argument map illustration may be useful, it might better be introduced as one of several techniques for diagramming arguments, and the argument in its original form presented first and then (by way of illustration) more fully explicated by the map.

This is a good point as well, there are certainly limitations with the argument map as a method of describing an informal argument and all other forms need to be presented, perhaps with the pros and cons of each one mentioned.

As regards to the paradoxes of material implication and relevance that you mention, for instance the begging the question fallacy of Nothing can go faster than light. Therefore, nothing can go faster than light, argument mapping deals with that through use of a device similar to the relevance criterion. These can be known as the "holding hands principle" (every significant term appearing in a co-premise must also appear in the conclusion) and the "rabbit principle" (every significant term appearing in the conclusion must also appear in the premise(s).

Thus by the rules of argument mapping, it is invalid to state something like Nothing can go faster than light. Therefore, nothing can go faster than light. or I am alive. Therefore If I am dead, then I am alive. Grumpyyoungman01 01:06, 19 April 2007 (UTC)

Material implication

Hello, again, GYM--I'm not sure how I ought to format a thread like this--just keep indenting? I'm not sure what you have in mind re. material implication--nothing I mentioned connoted that. The so-called paradoxes of material implication involve certain counter-intuitive aspects of the accepted truth conditions for the material (or, as it is also called, truth-functional) conditional. In part, these result from reading "if p, then q" as "p implies q," and then asking a question like, "Why should it turn out that p implies q just because p is false??" The problems, as you know, can be multiplied. Part of the solution is to note that to generate a "paradox," one must exploit an ambiguity of the word "implication," which tends to connote a strong logical connection. However, "implication," as defined in formal logic, doesn't mean the same thing as "if.., then---." "If p, then q" is false only when p is (materially) true and q (materially) false; A statement 'p' implies a statement 'q'(note, too, a grammatical difference--"If..., then---" is a connective, whereas "implies" is a verb, requiring nominal expressions on each side) is true just in case it is not possible for 'p' to be true while 'q' is false. There is a connective that expresses this relationship, referred to as the "fish-hook" symbol, called "strict implication."--jbessie 03:44, 19 April 2007 (UTC)

You are right, I don't see any mention by you of MI. I was lumping material implication together with things like Petitio Principii as an area where argument maps don't get confused as opposed to basic symbolic logic. On the other hand as already discussed there are many disadvantages with argument maps as opposed to formalisation. Some of this stuff probably belongs in the argument mapping article.

On a related matter, I don't have a good critical thinking/informal logic text. Just several bad ones, so you're recommendations are helpful. - Grumpyyoungman01 08:00, 19 April 2007 (UTC)

Ext. link

I added an external link about logical fallacies, which seems interresting to me (but I'm not an expert). Feel free to remove it if you think it is not appropriate here.--OlivierMiR 07:01, 2 June 2007 (UTC)

Remove argument map?

The argument map we are talking about is available at Image:Traffic_congestion_straw_man.png. How can I include a link here to this image (without displaying it in this page)?

The argument map is difficult to understand and lacks an explanation. I think this has already been said here above, but I'd like to add something.

Is the red "oppose" thing supposed to explain why the green argument is false? If yes, then there is a problem: the red part does not explain why the green part is false. Furthermore, the middle red sentence ("People would want to take the same number of trips (...) regardless of (...) roads (...)") is most probably false.

The green part (together with the conclusion) is incorrect because of the upper-right "support": "If people take more trips by car then traffic congestion will increase", which suppose that the roads number remains constant, and thus may not be used to support the conclusion which suppose that more roads are built.

I think that this argument map is either incorrect or misleading because of the lack of explanations. If nobody has time to rewrite the article, I propose to remove the argument map.--OlivierMiR 07:15, 2 June 2007 (UTC)

I agree.--jbessie 16:23, 2 June 2007 (UTC)

I added it as a thumbnail in a gallery and it was later enlarged. It is not necessary on this page, so I don't object to its removal. You are also right that the map is flawed in that the top right section supposes the number of roads remaining constant, whilst its co-premise asserts a case based on the number of roads increasing. This is very annoying, let me know if you figure out how it can be fixed.

Note that whether the middle red box is true or not does not alter either the argument's status as an example of the fallacy of the strawman or the argument's validity/invalidity - not that that is explained here. Could you please explain in more detail why you think that the objection (red part) does not properly explain why the green box above (the straw man) is false? - Grumpyyoungman01 06:26, 4 June 2007 (UTC)

If I understand well, this argument map illustrates that the "green guy" is victim of a straw-man argumentation? As I understand now, the "red guy" is argueing against the green support argument low-right, and "forgets" to argue against the green support argument low-left. I had not understood that when I first commented this article. So the red box correctly explains why the green box above is false (I didn't express myself correctly).

Following discussion on page Straw man.--OlivierMiR 14:55, 12 June 2007 (UTC)

Add some text to the article if you think it will help explain things. - Grumpyyoungman01 06:57, 13 June 2007 (UTC)

I agree wholeheartedly with OlivierMiR. - DMCer (talk) 18:58, 5 December 2007 (UTC)

You can't rely on this as an explanation: Φ

I've removed this:

"Could have an extra premise added such as:

For any X and for any Φ, if X is P and X is Φ, then all P's are Φ"

This is an encyclopedia for the general public, not a math book. If there's anything worth saying there, can someone add the information to the article in a way understandable to the general public? Thanks. Gronky 14:11, 16 July 2007 (UTC)

Definition

The current definition given for an informal fallacy is "an argument whose stated premises fail to support its proposed conclusion". Doesn't that make every inductive argument an informal fallacy? But then the page goes on to say that inductive arguments can be convincing, even if they are informal fallacies. So--what makes something an informal fallacy? Is an informal fallacy just an unconvincing argument? — Preceding unsigned comment added by 46.37.62.241 (talk) 22:20, 16 July 2013 (UTC)

Article fail.

The article is about "informal fallacies." But then the body of the article describes "formal fallacies," and "inductive fallacies," and never mentions "informal fallacies." I'm left to surmise (perhaps incorrectly) that an "informal fallacy" is synonymous with an "inductive fallacy." Is that correct? — Preceding unsigned comment added by 2602:30A:C08C:A6F0:21C:B3FF:FEC3:2572 (talk) 12:26, 12 August 2013 (UTC)

Duplication

I wanted to point out there is some duplication between the topic of this article and a section in another article. There is more content in the other article. See: https://en.wikipedia.org/wiki/List_of_fallacies#Informal_fallacies Xblkx (talk) 02:35, 9 January 2014 (UTC)