Talk:Affirming the consequent

message: Affirming the consequent is just the opposite to modus tollens, right? how is it called?
:How's what called? modus tollens? Evercat 18:38 14 Jun 2003 (UTC)
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I removed: If there is fire here, then there is oxygen here.  (Since oxygen is required for fire.)
It was not needed and interfered with understanding the article. Also, it itself is fallacious, as it begs the question of how the sun burns, because there is no oxygen in it. -- Corey 21:31, 6 Sep 2003 (UTC)
replies: text: But the sun isn't fire.  It's a nuclear reaction.  :P --Tiberius47 06:43, 12 December 2006 (UTC)
thread_title:  Etc. 

message: This article seems to have the definition backwards. It currently states, "The fallacy of affirming the consequent occurs when a hypothetical proposition comprising an antecedent and a consequent asserts that the truthhood of the antecedent implies the truthhood of the consequent." But in fact, the truthhood of the antecedent does imply the truthhood of the consequent. The fallacy occurs when a proposition asserts that the truthhood of the consequent implies the truthhood of the antecedent. I'm going to make the change unless someone objects. - Walkiped 01:30, 1 Dec 2004 (UTC)
thread_title: Backwards definition

message: An automated Wikipedia link suggester has some possible wiki link suggestions for the Affirming_the_consequent article:
* Can link Stephen King: ...mple. Here is an argument that is obviously incorrect:  :If Stephen King wrote the bible (P), then Stephen King is a good writer (Q)...
Notes: The article text has not been changed in any way; Some of these suggestions may be wrong, some may be right.
Feedback: I like it, I hate it, Please don't link to — LinkBot 11:31, 1 Dec 2004 (UTC)
thread_title:  Suggest 1 possible wiki link for [[Affirming the consequent]]. 

message: I recall an episode of the simpsons that involved a bear patrol using this argument as a joke, where Lisa says that the fact that there aren't any bears nearby isn't neccessarily a result of the bear patrol, just as the absence of tigers couldn't be said to be a result of a particular rock.  Can the appropriate part of the script be included as an example?--Tiberius47 06:43, 12 December 2006 (UTC)
thread_title:  Popular culture examples

message: Since we tend to use the word 'someone' almost exclusively in reference to humans, perhaps we could clarify Premise #1 below as follows:
If someone one is human (P), then she one is mortal (Q).
Anna is mortal (Q). Therefore Anna is human (P). --Ryan Mahoski 16:17, 12 January 2007 (UTC)
thread_title:  Anna syllogism 

message: This entry teems with needless jargon, when the concept is a simple formal pattern.  Unless someone out there can provide a good justification for verbiage such as "bidirectionality" and such, I'm going to be bold and simplify this article. 271828182 23:25, 9 February 2007 (UTC)
replies: text: Go ahead mate.  Trim off the fat.  Dbuckner 13:11, 10 February 2007 (UTC)
thread_title:  Overly wordy  

message: This article should be revised to explain the difference between formal validity (which is defined in terms of the syntactic features of the argument) and the related semantic notion of validity (which is defined in terms of the move from the premises to the conclusion being a truth preserving one, or in terms of a counterfactual like, "if the premises were true, then the conclusion would be true also).
The important difference is easy to see in arguments like this:
1) If Mark Twain wrote "Huckleberry Finn" then Mark Twain is a good author.
2) Mark Twain wrote "Huckleberry Finn."
3) So, Mark Twain is a good author.
1') If Mark Twain wrote "Huckleberry Finn" then Mark Twain is a good author.
2') Samuel Clemens wrote "Huckleberry Finn."
3') So, Mark Twain is a good author.
Since Mark Twain and Samuel Clemens are the same person, the second argument is (informally) valid.  That is, if its premises are true, it's conclusion is also.  However, it is not formally valid because the success of the inference depends on the semantic interpretation of "Mark Twain" being the same as that of "Samuel Clemens."  The first argument on the other hand, will be truth preserving under any assignment of values to terms.
This only matters insofar as the current discussion of arguments instantiating multiple argument forms is confusing, and does not adequately explain why some instances of affirming the consequent are valid arguments (that reason being that an additional but uncontroversial premise can be added to those arguments which would then make them formally valid.  For instance, in the second argument above, it would be something like "Mark Twain is Samuel Clemens" or maybe, "If Samuel Clemens wrote Huckleberry Finn then Mark Twain wrote Huckleberry Finn" (which can then be used to conclude the antecedent of (1') etc. etc.
:You are right to point out that the current version of the article does not distinguish between syntactic and semantic validity.  In defense of the current version of the article, however, I would say it's not necessary to delve into such fine details given the basically simple nature of the fallacy.  Someone who comes to this article wondering what "affirming the consequent" means would likely be baffled to no good purpose by a distinction largely irrelevant to the informal contexts in which this fallacy almost always exists.  The only reason I included any mention of the technical point at all is to avoid making a statement which is flatly false, as would result if we removed the first parenthesis from the article.  Also, I'd say the existing paragraph on this technicality is less confusing than, say, the explanation you've given above (no offense intended). 271828182 16:59, 8 June 2007 (UTC)
replies: text: Tweaked article for better (IMHO) explanations. --Kjoonlee 04:43, 9 June 2007 (UTC)
thread_title:  Validity 

message: I think that there should be a mention about the fact that modern medical diagnosis relies very heavily on analysis of symptoms.
The condition causes the symptoms,
The patient has the symptoms,
Therefore the patient has the condition.
Of course this is vastly generalised, and medical doctors usually consider a number of possibilities, and never act until they have examined the possibilities, but they do use this to rule out a vast majority of conditions, and often a particular list of symptom is specific to a particular condition. Perhaps the limitations of this logic should be discussed in terms of real world examples.
thanks Glooper (talk) 09:00, 11 March 2008 (UTC)
replies: text: That's essentially "inference to the best explanation", more commonly known as (educated) guessing.  I think the link to the IBE article is sufficient.  If we discussed every common situation where AffCon crops up, the article would be too noisy.  Besides, one of the examples is already a case of diagnostic reasoning!  271828182 (talk) 03:19, 12 March 2008 (UTC)
thread_title:  Medical diagnosis 

message: The article says:
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Arguments of the same form can sometimes seem superficially convincing, as in the following example:
If I have the flu, then I have a sore throat.
I have a sore throat.
Therefore, I have the flu.
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But teaching people how this argument will really come up in the real world should read like this:
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Every time I have the flu, it always makes my throat sore.
I have a sore throat today, so that means I must have the flu.
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Not being an expert in this field, I don't want to edit the actual article.  But if my suggestion doesn't violate the rules of the fallacy, then please add it to the article.  —Preceding unsigned comment added by 69.3.198.122 (talk) 19:01, 17 August 2008 (UTC)
thread_title:  We should make the real world example quotes sound more like the way people actually speak. 

message: I don't see how having more than a couple examples makes the article better.  If someone is coming to this article, they want or need an explanation of a basic concept in informal reasoning.  Making it longer than necessary serves no clear purpose except to waste time.  If you want a reference, try Strunk & White, The Elements of Style, or Orwell, "Politics and the English Language".  I will note that User: Loodog has offered no justification for including the extra words besides saying "it's better". 271828182 (talk) 18:01, 11 September 2009 (UTC)
replies: text: It's clearer.  The reason that p->q does not necessitate that q->p is not obvious to most people.  And it perfectly sets up the later section about if and only if.--Louiedog (talk) 19:01, 11 September 2009 (UTC)
replies: text: It's not only less concise, it's wrong.  A conditional is not necessarily a causal statement, which the current explanation implies. 271828182 (talk) 23:22, 11 September 2009 (UTC)
replies: text: Fixed.--Louiedog (talk) 16:00, 12 September 2009 (UTC)
thread_title:  concise vs. flabby prose 

message: The climate change example is an oversimplification of the scientific arguments underlying climate research. Even if the example as written is logically correct, it is factually false or at best misleading because it clearly implies that climate scientists simply looked at two sets of data (global temperature increases and CO2 emissions increases) and drew a definitive conclusion and closed the case. The hypothesis is that increases in carbon dioxide affect the temperature of the earth. Humans produce prodigious amounts of carbon dioxide and that there is a distinct and clear correlation between the increase in carbon dioxide emissions and the increase in global temperatures. No other viable competing cause can be found to explain the increase in global temperatures (asteroid hit, sudden, large amounts of volcanic activity). Where is all the CO2 coming from?  If this is the logical fallacy of affirming the consequent, then so is placing a pot of water on the stove, turning on the burner and predicting that the consequent boiling of water affirms that the heat of the burner is the cause. If you are going to use a real-world example, it should be a sound one, and not one that promotes a political agenda (whether intended or not).
General Ludd (talk) 16:02, 4 August 2010 (UTC)
replies: text: Absolutely right.  Global warming is not much contested in the scientific consensus, and is an awfully political issue that detracts from the content of the logical argument.  Since all of science essentially relies on affirming the consequent, better to apply it to something less contested politically.  I've changed the example to General Relativity and the observed Mercury Perihelion shift.--Louiedog (talk) 18:44, 4 August 2010 (UTC)
replies: text: Why not give a simple example requiring no specialist scientific knowledge. The purpose of examples is to make a point easier to understand, not to introduce additional complexities Philogo (talk) 01:43, 15 January 2011 (UTC)

text: if you look at Scientific method#Introduction to scientific method you will see that scientific metnod is CONTRASTED with affirming the consequent.  After all it would strange, to say the least, were scientific advance be based upon the application of a fallacy.  
Philogo (talk) 02:44, 15 January 2011 (UTC)
thread_title:  Use of the fallacy in science--climate change example 

message: I do not think that the following part of the article is correct:-
If claims P and Q express the same proposition, then the argument would be trivially valid, as it would beg the question.
An argument schema is said to be valid if and only if the premises cannot be true but the conclusion false.  That it to say the schema is valid if the Corresponding conditional (logic) is a logical truth.    It does not make a lot of sense to say an argument scheme is valid "when" the premises have a given interpretation.  
Consider the argument schema P therefore Q.  This is clearly invalid becasue it can have a true premiss but a false concusion.  It would be  surely to misu----Philogo (talk) 14:31, 14 November 2010 (UTC)
replies: text: I suspect the confusion has crept in after numerous edits by disparate hands.  The sentence you quote is indeed incorrect if you take "the argument" to refer to "the argument schema", but the writer probably meant an argument token.  The whole article has become infested with weeds and mold and should be cleaned up and shortened. 271828182 (talk) 23:57, 13 November 2010 (UTC)

text: I suggest the deletion of the para Tautologies and the follwoing if and only ifPhilogo (talk) 14:31, 14 November 2010 (UTC)
replies: text: Have now deleted offending txtPhilogo (talk) 20:02, 3 December 2010 (UTC)
thread_title:  Tautologies 

message: An example I heard from a college philosophy class:
* Caterpillars eat cabbage. Catherine eats cabbage. Therefore, Catherine is a caterpillar.
This same "logic" is regularly used to assign incorrect labels and intentions, usually moral or political, to individuals and groups:
* The Nazis implemented strict gun control laws. Liberals favor strict gun control laws. Therefore Liberals are [like] Nazis.
* The Nazis relied on a strong military. Conservatives favor a strong military. Therefore Conservatives are [like] Nazis.
— Loadmaster (talk) 22:21, 16 March 2011 (UTC)
thread_title:  Other examples 

message: * Does not add to the article
* One was itself fallacious (Fallacy fallacy)
* The second was an example of a different type of fallacy
* Was unnecessarily political in nature
The provided reference was a quote of a quote of an alleged quote taken out of an out of print reference source and heavily butchered with the use of several ellipses. Please use first-hand sources in any future references you provide, preferably ones that can be followed up on and verified.
Pointing out that a particular creed or worldview has apologists  from half a century ago who sometimes make fallacious statements seems like something more suitable for a history article. If you would like to enrich Wikipedia by starting an article about the history and evolution of Baptist doctrine and theology, that would be a a useful contribution. Political axe grinding does not, however, belong in a scientific reference article.
- DevAudio (talk • contribs) 17:50, 1 September 2011 (UTC)
thread_title:  Removed the anti-religious and fallacious example, twice

message: This page was tagged as stub in November 2008. Please help expanding this page. -- Magioladitis (talk) 17:02, 9 August 2012 (UTC)
replies: text: Expanding the article is a good idea, but I don't see why the date parameter needs to be removed in the meantime, so I have restored it. The parameter is not broken, Mediawiki allows any parameter to be used on any template without ill effects. — Carl (CBM · talk) 17:37, 9 August 2012 (UTC)
thread_title:  Stub 

message: Substituted at 19:44, 1 May 2016 (UTC)
thread_title: Assessment comment

message: Formally the "rain" example is correct. However the real-life reasoning about rain is not fallacious per se. In fact, just the opposite: it is an example of a reasonable deduction. When I look out of the window and I see the wet driveway, I am not going to conclude there must have been a stampede across my yard and now it is covered in cattle piss. Rain is the overwhelmingly most common reason of my driveway becoming wet, therefore my reasoning is sound, and not at all fallacious.
The "Fort Knox" is not a good example for the lede either: it is an obvious nonsense. A good example  must be the one where a person indeed may fall into a trap of fallacious reasoning. 
See also the first ref (from Fallacy Files). Staszek Lem (talk) 19:48, 30 August 2018 (UTC)
thread_title:  Bad example in the lede 

message: Why should affirming the antecedent given the consequent be called affirming the consequent? "Affirming the consequent" should mean the fallacy of saying "(A -> B) => B", not of saying "(A -> B) => (B -> A)". Philgoetz (talk) 02:15, 18 March 2019 (UTC)
thread_title:  Affirming the antecedent is not, in fact, affirming the consequent 

message: (Talking about this version, current now) It contradicts the formal description: the latter says nothing about "conditional". Therefore the def must have a reference. Also as a result of this the example is clumsy. - Altenmann >talk 17:16, 11 December 2023 (UTC)
replies: text: Strictly speaking, the lead does not need a reference if it summarizes sources material in the body of the article, see MOS:LEADCITE. One could check the references of the first paragraph of the section "Formal description". An indicative conditional is an "if-then" statement. This type of statement is described in the lead. One difficulty may be that the text uses various technical terms without explaining them. Phlsph7 (talk) 09:05, 13 December 2023 (UTC)
replies: text: Strictly speaking everything needs a reference. No, this lede does not summarize the body, hence the  objection in my post, which you failed to address. - Altenmann >talk 17:16, 13 December 2023 (UTC)
thread_title:  Bad definition in the lede