Talk:Affirming a disjunct

message: Isn't 0 both even and odd, under particular circumstances?
"The sun always shines somewhere."
This is not necessarily true.  —Preceding unsigned comment added by 82.93.160.17 (talk) 23:34, 17 November 2007 (UTC)

message: The article incorrectly refers to the example of Max the Cat as being invalid. While the argument is unsound, it is nevertheless valid. The truth-value of propositions determines soundness of an argument, not validity. The argument, as provided, is valid insofar as the premises, if true, make it impossible for the conclusion to be false. I have edited "invalid" to read "unsound."  — Preceding unsigned comment added by 2602:306:3275:E3F0:B8F1:495E:CE5D:4357 (talk) 19:33, 1 August 2015 (UTC)
thread_title: Example

message: In the first example the article employs "and/or"...I'm new to Wikipedia--and haven't taken a lot of logic--but I would have assumed that it would be better to merely use "or" since or is presumed to be inclusive. Also, should it be formalized? I'll wait a few days for comments on both these points. Frayr (talk) 13:37, 29 July 2009 (UTC)
thread_title: Usage

message: Since this article is meant to inform people who are not educated in formal logic, I thought I should point out that in common usage " A is true or B is true" does indeed imply one or the other, not both, are true.
  If mom says "do this or that will happen" it clearly implies that both will not be true.
  If a person says "I am at home or I am in the city" in normal conversation it is considered a clear indication that both are not true.  — Preceding unsigned comment added by Thelarrykennedy (talk • contribs) 12:53, 3 April 2017 (UTC)
thread_title:  Affirming a disjunct / common usage 

message: Some other fallacy pages have an opposite mentioned. Is there no opposite of Affirming a disjunct?
Whereas this page is about confusing OR with XOR, would the opposite be confusing XOR with OR?
E.g. affirming a disjunct..
.. Max is a mammal or Max is a cat (OR written)
.. Max is a mammal
.. Therefore, Max is not a cat (XOR assumed)
Opposite would be?..
.. Max is an elephant or Max is a human (XOR written)
.. Max is an elephant
.. Max can still be a human (OR assumed) Wallby (talk) 11:58, 13 December 2023 (UTC)
replies: text: There is: denying the antecedent. In mathematics and logic, you need to show it's an iff ("if and only if") statement for both statements to imply each other, therefore implying a negation of one implies a negation of the other. Otherwise you incorrectly conclude the negation of the antecedent by observing the negation of the consequent JohnAdams1800 (talk) 03:49, 7 January 2024 (UTC)
thread_title:  No opposite? 

message: I added two books as sources: 
1. Introduction to Analysis with Proof by Steven Lay at https://www.vitalsource.com/products/analysis-with-an-introduction-to-proof-steven-r-lay-v9780321998149
2. Discrete Mathematics and its Applications by Kenneth H. Rosen at https://www.vitalsource.com/products/discrete-mathematics-and-its-applications-kenneth-rosen-v9781259731709
I used the Amazon links for the sources because Amazon is more frequently used to buy books, but these links show the table of contents for both books, which cover logic and set theory, including this fallacy which can be showed via say truth tables or Venn diagrams (special case of Euler diagrams). JohnAdams1800 (talk) 03:47, 7 January 2024 (UTC)
thread_title:  I added sources, as an expert in logic (Master's student in mathematics & statistics)