Talk:Relevance logic

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Relevant vs relevance[edit]

I propose we change the preferred name to relevance logic. Pro:

  1. It is the spelling prefered by the standard-setting Stanford Encyclopedia of Philosophy
  2. It is the term preferred in the topic defining Anderson and Belnap
  3. It is marginally more popular according to google:
    • "relevant logic" -> 2900 hits, and 30 for intitle:"relevant logic"
    • "relevance logic" -> 3090 hits, and 56 for intitle:"relevance logic"

I concur. Further pros:

  1. Most of the prose in this article is mine anyway; I developed a stub that already existed under "Relevant", though I'd have preferred "Relevance." Does that give my opinion some weight?
  2. Those google stats probably understate the matter: "relevant logic" can also occur as a modified common noun rather than as a proper name, as in: "In order to research his paper, he read through all the relevant logic texts." All the logic texts, that is, relevant to his paper. User:


  1. Conservatism ---- Charles Stewart 20 Oct 2004

"Details need to be filled in"[edit]

Where someone wrote "Details need to be filled in", is that part of the description of how relevance logic works, or is a meta comment, as suggested by the italics. Meta-comments should instead be tags, right? If you think it was meant to be a meta-comment, would someone please change it to the appropriate wiki tag. Feel free to delete this talk section once resolved. --2602:306:C414:CA30:4C99:3DEC:BD30:794A (talk) 19:17, 21 March 2016 (UTC)

Thanks for pointing that out; I've converted it into a wiki comment for future editors. --Mark viking (talk) 20:16, 21 March 2016 (UTC)

What is missing?[edit]

Could we please have a section on which axioms of classical logic are excluded from relevance logic! In particular, implicational propositional calculus uses modus ponens (which is included here) and the axiom schemas:

  • P → (QP)
  • (P → (QR)) → ((PQ) → (PR)) and
  • ((PQ) → P) → P.

So I would be especially interested in these schemas — which of them are not allowed in relevance logic? And why? JRSpriggs (talk) 19:43, 17 August 2018 (UTC)

Two more schemas from an alternative axiomatization:

  • (AB)→(A→(CB)) and
  • A→((BC)→((AB)→C))

would also be of interest to me. JRSpriggs (talk) 20:39, 17 August 2018 (UTC)

It might make more sense for that to go in a paragraph or subsection of the Axiom system section. It could only feasibly comment on a few axioms from relatively common axiomatizations of classical or intuitionistic logic, such as the initial three above. Inferential (talk) 10:14, 2 January 2019 (UTC)

Simple characterization of relevance logic[edit]

In paraconsistent logic#Relation to other logics, it gives a simple characterization of relevance logic which I do not see in this article. To wit, "A logic is relevant iff it satisfies the following condition: if A → B is a theorem, then A and B share a non-logical constant.". Is this correct? If so, should we not add it to this article? JRSpriggs (talk) 20:56, 17 August 2018 (UTC)

This is the variable sharing principle and it is considered to be a necessary condition for relevance. Edwing Mares author of the Relevance Logic article at SEP, says that some additional semantic criterion is necessary ( I think there are quite a few logicians, especially proof theorists, who treat the variable sharing principle as sufficient. — Charles Stewart (talk) 15:44, 19 August 2018 (UTC)

Merger proposal[edit]

I propose that Strict_logic be either merged into Relevance_logic, or deleted.

Strict_logic does not include any citations and has largely been that way since 2014.

Pinging users who have edited Strict_logic @Username Needed, 123qweasd, Paraconsistent, CBM, Andrew Eisenberg, and Charles Matthews: Please weigh in on this merge proposal.

Poll (select any combination of Merge, No, or Delete)

  • Merge or DeleteStrict_logic contains nothing of substance, in the first sentence it states "Strict logic is essentially synonymous with relevant logic [...]". -- Chris James Hall (talk · contribs)
  • No -- That first clause is contradicted by the rest of the content of the article. It says "ordinary logic without Disjunction introduction", but this article specifically allow disjunction introduction. It also says "linear logic with contraction", but relevance logic lacks many features of linear logic specifically the many varieties of operators. Indeed, these two parts of the article appears to contradict each other, suggesting that the article is incoherent and should be deleted. JRSpriggs (talk) 01:46, 27 November 2018 (UTC)
  • Delete -- As JRSpriggs pointed out, the article starts out with incompatible claims. There is not much to the Strict Logic article. There are no citations provided in the article. A quick google search does not reveal any sources on strict logic, apart from that wikipedia article. Inferential (talk) 10:02, 2 January 2019 (UTC)