Talk:Logical consequence/Archive (Logical implication)

message: What the hell is the difference between Logical implication and the Material conditional ????? I propose a merge. Fresheneesz 07:35, 11 October 2006 (UTC)
replies: text: Actually both pages are a mess. Nortexoid 06:04, 10 December 2006 (UTC)
replies: text:  Actually, interwiki links are a mess here. --VictorAnyakin (talk) 11:50, 21 April 2008 (UTC)
thread_title: Material implication

message: The introduction of the article had been changed to read:
:Logical implication is not to be confused with material implication (AKA material conditional). 
:
:In ordinary language, material implication is often expressed by sentences of the following form:
:
:* If P then Q.
:Here P and Q are propositional variables that represent propositions in a given language.  In a statement of the form "if P then Q", the first term, P, is called the antecedent and the second term, Q, is called the consequent; and the statement as a whole is called a conditional.  Assuming that the conditional is true, then the truth of the antecedent is a sufficient condition for the truth of the consequent, while the truth of the consequent is a necessary condition for the truth of the antecedent.
:
:A sentence is valid (not to be confused with the property of an argument being valid) if and only if it is true on every interpretation. (See also logical truth, tautology.) 
:
:A logical implication is a valid material implication. 
:
:The rest of this article appears to be about material implications. 
I found this introduction confusing, since it looks like discussion of the article rather than an introduction to the article.  So I replaced the introduction with an earlier version.  The above introduction is probably salvageable if it is modified to stop talking about what shouldn't be confused and start talking about what is to be understood. Michael Slone (talk) 23:52, 9 December 2006 (UTC)
thread_title: Introduction

message: They are exactly the same concept, so why are there two distinct pages for them? This one is actually quite poorly written. I like the introduction though. Just kidding, I wrote it. This page should be scrapped (except for the great intro.) and redirected to Entailment. Is anybody going to make a stink about it if I do it? Nortexoid 23:38, 6 January 2007 (UTC)
replies: text: Now that I've drastically edited the article, I don't think a redirect is in order, but rather a merge is. There is some useful information in the Entailment article that could be placed in this one, and then Entailment could be redirected to this article. Nortexoid 01:46, 7 January 2007 (UTC)
replies: text:  I'll support a merge, without really knowing much about entailment. I'll trust your judgment. Fresheneesz 21:49, 7 January 2007 (UTC)
replies: text: I support a merge, or just redirect--Philogo 13:19, 5 December 2008 (UTC)
replies: text:  Sorry, I reverted the redirect. I disagree with a redirect without first merging the material. If anything, Entailment should rd here. This page has more information and better pictures. Fresheneesz (talk) 00:57, 6 December 2008 (UTC)
replies: text:  I merged the articles as best I could and replaced the redirect. Entailment is in dire need of work. There is even a section in entailment on how it is and isn't the same as logical implications.... I'm gonna leave that up to someone else to fix. Fresheneesz (talk) 01:20, 6 December 2008 (UTC)
replies: text:  I should point out that it is semi-standard in the literature to take logical implication to be the syntactic notion of derivability (of sentences from sets of sentences) and entailment the semantic notion of truth preservation (from sets of sentences to sentences). In this case, a merge is inappropriate, and so I retract my previous suggestion. Nortexoid (talk) 22:00, 6 December 2008 (UTC)
replies: text:  Gah, well wonderful. Would you be willing to fix the damage I caused then? Fresheneesz (talk) 00:24, 7 December 2008 (UTC)
replies: text:  Apologies. I made my initial suggestion nearly two years ago, when I was a fool. I believe, optimistically, that I'm becoming less of a fool as the years pass. In any case, would it not suffice to simply undo the last few edits to get back to the original (on both the pages for entailment and logical implication)? I would be more comfortable if someone else did it. Nortexoid (talk) 09:30, 7 December 2008 (UTC)

text: I have redirected this article to Entailment since (a) we do not need two articles on the same subject (b) Entailement has the better material (c) Entailment is (IMHO) a better title cos folks are confused enough about implicatiions as it is.  If any materail was in this article that would enhance Entailment then it can cut and pasted across. OK?--Philogo 13:53, 9 December 2008 (UTC)
replies: text: It does not appear to redirect now.  Does anybody think that Logical Implication is anthing other than Entailment? If so, what is the difference? If not,  what reason can there be for having two articles on the same subject?Philogo (talk) 17:50, 15 November 2010 (UTC)

text: I will support a merge, however please make sure it is under either the "logical connectives" or "logical consequence" category.Greg Bard (talk) 18:38, 15 November 2010 (UTC)
replies: text: Go aheadPhilogo (talk) 14:06, 17 November 2010 (UTC)
thread_title: Possible merge with [[Entailment]]

message: I wrote this: p → q ≡ p ∧ q ∨ ¬p ∧ ¬q ∨ p ∧ ¬q
It helped me understand the implied operator. Might it help improve the article, if someone could perhaps help me get it out of unicode into that fancy formulae format that wikipedia uses? --Nerd42 (talk) 03:29, 14 October 2009 (UTC)
thread_title:  p → q ≡ p ∧ q ∨ ¬p ∧ ¬q ∨ p ∧ ¬q 

message: Logical implication can be confusing without a simple explanation of the concept that it is supposed to formalise. The exisiting article is difficult even for some experienced specialists:
http://en.wikipedia.org/wiki/Logical_implication
Logical implication can be used in many professions. Uses include:
* Establishing proof about certain aspects of software design procedures.
* Writing technical manuals for software.
* Writing universal and existential quantifications which can readily be converted into code loops.
* Helping to ensure code is correct - that is, for the debugging of code. It can be used in preconditions, midconditions, loop invariant conditions and postconditions of method specifications.
Currently there are several pages for the same thing, and confusion amongst the authors. This suggests that the fundamental concept of logical implication is not properly understood. Here are some comments from the 'talk' page:
-------------------------------------------------
"What the hell is the difference between Logical implication and the Material conditional ????? I propose a merge."
"... both pages are a mess"
"... interwiki links are a mess here"
"... The above introduction is probably salvageable if it is modified to stop talking about what shouldn't be confused and start talking about what is to be understood"
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I added a simple explanation of 'logical implication' to the 'Logical implication' page. I think that logical implication has a real world origin, although this may not be verifiable.  —Preceding unsigned comment added by DavidMortimer (talk • contribs) 09:15, 6 April 2010 (UTC)
thread_title:  A simple explanation 

message: Please see Talk:Entailment#Duplication of content. - dcljr (talk) 19:51, 15 January 2011 (UTC)
thread_title: merged into entailment