Talk:Fallacy of the undistributed middle

Affirming the Consequent
Is there an example of an undistributed middle fallacy that doesn't result in affirming the consequent? kostmo 01:25, 10 July 2006 (UTC)

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How about the following:

Some M is not P

All S is M

Thus, No S is P

--23.17.148.104 (talk) 04:06, 31 March 2012 (UTC)

Erasmus Montanus
In the comedy Erasmus Montanus by Norwegian/Danish playwright Ludvig Holberg, the farmer's son Erasmus visits his parent's farm while studying Latin and stuff at the university. To his mother: ''A stone cannot fly. Little mother cannot fly. Ergo, little mother is a stone.'' His mother, unhappy with the outcome, starts to cry. - To me (as a Dane), this is the obvious example of the fallacy. If someone not Danish likes it too, please add it to the article...--Niels Ø 20:18, 17 November 2006 (UTC)
 * I'm 13 years late, but if you have a citation, why not add it? xRENEGADEx (talk) 06:41, 19 May 2020 (UTC)

Examples
Does the example mentioning Eric Harris and Dylan Klebold seem verbose and even disconnected to anyone else? Further, isn't there a name other than "John Doe" that more appropriately fits there? 64.90.198.6 00:08, 13 December 2006 (UTC)
 * Kimveer Gill? V-Man737 08:02, 14 December 2006 (UTC)

I think this and Undistributed middle can be merged.

Alparsla 09:00, 16 April 2007 (UTC)

Fallacy of the undistributed middle for dummies
This article (what with all it's logicianese) seems unnecessarily complex. In the simplest possible terms, is not the fallacy of the undistributed middle the mistake of failing to account for exceptions to the general premise of a syllogism, of which the minor premise is one such exception, leading to a false conclusion?

In the example:

Ostriches have two legs. I have two legs. I am an ostrich.

The general premise implied is: All two-legged things are ostriches. One overlooked exception (the second premise: a man) leads to the false conclusion. —Preceding unsigned comment added by 124.62.255.251 (talk • contribs)
 * It is mistaking a premise of the form "P implies Q" ($$p \implies q$$) for "P if and only if Q" ($$p \equiv q$$); i.e. mistakenly thinking that, knowing only that P implies Q, then Q implies P as well. What DOES follow is that NOT Q implies NOT P ($$\neg q \implies \neg p$$). Thus:: I do not have two legs, ergo I am not an ostrich. Grandfather does not carry a backpack, therefore I know he is not a student. 2601:545:8201:6290:D8AE:747:15B5:9F0E (talk) 09:55, 28 February 2021 (UTC)

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It is hard to believe that this is still regarded as a fallacy for the reason stated: that the middle term is 'undistributed'.

I'd have thought that Geach's writings on this subject would have laid this haory old logical error to rest by now.

Geach, P. (1972), Logic Matters (Blackwell).

Geach, P. (1980), Reference And Generality (Cornell University Press, 3rd ed.).

Rosa Lichtenstein (talk) 21:58, 24 February 2008 (UTC)

Clarification
Is this similar to the Continuum fallacy?

What are these errors?
Witches can burn.

Wood can burn.

Ergo, witches are made of wood.

Wood floats in water.

Ducks float in water.

If someone weighs the same as a duck:

(possibly ergo, (s)he floats in water)

Ergo, (s)he is made of wood,

ergo, (s)he is a witch!

141.158.64.33 (talk) 10:04, 19 July 2010 (UTC)
 * When it comes to witches, such errors don't count. It's a fair cop. ;-) 2601:545:8201:6290:D8AE:747:15B5:9F0E (talk) 10:00, 28 February 2021 (UTC)

Classical Formulation
It seemed like this article was lacking the simple answer to the question of what is a undistributed middle term. The pattern section has fancy graphics but only comes near an answer. I added the classical formulation section because it is the answer strictly speaking. I moved it to be the first section because I think it is what people are looking for in this article. I would delete the Pattern section but did not want to make too radical changes without some consultation. 68.193.85.16 (talk) 04:58, 19 September 2011 (UTC)


 * I agree that these graphics don't help. When trying to understand this, thinking in sets helped me a lot, and as such, Venn Diagrams might help as an illustration. Take this simple example. The big empty circles are groups of people and the small filled circles are people. The big circles are arranged by the statement "All students carry backpacks". Grandpa is placed by the statement "Grandpa carries a backpack". However, it is pretty obvious that you will need some more argumentation in order to conclude "Grandpa is a student" from this image. I placed Fred in there, because you could demonstrate the correct conclusion easily: "All students carry backpacks, fred is a student, therefore fred carries a backpack". Finally, note that such diagrams could be used to illustrate the various distribution relations, too. Tetha (talk) 12:36, 18 October 2011 (UTC)


 * I have an example which I think most people can understand: All texts are expressed via languages. Languages are man-made. Therefore, all texts are man-made. A religious person, a person who once was religious or a person who understands (one or more) religions will at once grasp the meaning of this fallacy; The Bible, for example, is believed, for some people, to not be man-made and they will thus grasp the context of the fallacy fairly quickly. Just a thought I had when I read this article. 84.234.243.219 (talk) 13:43, 9 June 2013 (UTC)

Add Venn diagram to clarify examples
On section Classical formulation, two examples are shown. The first example says:


 * 1) All Z is B
 * 2) All Y is B
 * 3) Therefore, all Y is Z. This syllogism is actually invalid

The second example says:


 * 1) All Z is B
 * 2) Some Y is Z
 * 3) Therefore, all Y is B. This syllogism is actually invalid

I think using a Venn diagram could clarify these examples by illustrating the first two statements. For the first example, it would be:



For the second example, it would be:



Is this correct? If so, I think it would be helpful for the reader to see these diagrams. I just made them in Google Keep, but somebody else could make them more beautiful.

As a side note, I have no knowledge on this topic. I found this article because a Wikipedian pointed out a mistake I made while editing another article; my mistake was related to this topic.

--Alej27 (talk) 03:11, 18 November 2020 (UTC)