Talk:Predicate (mathematical logic)
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[edit]Any chance of anyone explaining this so the average reader could get an understanding of what it means? Tyrenius 18:46, 24 October 2006 (UTC)
- Follow the new external link for an explanation.
S Sepp 14:04, 26 October 2006 (UTC)
- Thanks for the reference, but that's hardly an acceptable solution to a poor article. Hoping someone actually has this on their watch list and notices that the problem still exists. MJKazin (talk) 18:34, 23 April 2008 (UTC)
Merge
[edit]See Talk:Predicate (mathematics). --Abdull 11:04, 3 December 2007 (UTC)
See Talk: Predicate variable. Sae1962 (talk) 07:27, 2 March 2011 (UTC)
- Don't merge. Cleanup instead. There's a lot of confusion between the articles on propositional logic, first-order logic, term algebra, model theory, type theory, philosophy, general mathematics, and semantics(?). All have similar-but-different notions of predicates, but differ sharply in the details. I tried to clean up this article to make this clear, but I believe it has a loooong way to go. linas (talk) 17:05, 9 June 2011 (UTC)
Atomic formula
[edit]The follwoing in the article does not accord with Atomic formula and is surely wrong
- In first-order logic, atomic formulae are called predicate variables. [citation needed] A predicate can take the role as either a property or a relation between entities. When P is a predicate on X, one sometimes says that P is a property of X.
— Philogos (talk) 22:07, 16 June 2011 (UTC)
- There were a lot of problems with the text, but I think I have removed most of them. — Carl (CBM · talk) 02:03, 17 June 2011 (UTC)
Confusion
[edit]Thus seems confusing:
- Informally, a predicate is a statement that may be true or false depending on the values of its variables.[citation needed] It can be thought of as an operator or function that returns a value that is either true or false.
better sruely would be
- Informally, a predicate is an operator or function that returns a value that is either true or false. depending on the values of its variables.
- I think it's better to say something like "a predicate can be represented by a function that ...". This avoids using the word "is" about the predicate. — Carl (CBM · talk) 02:40, 17 June 2011 (UTC)
- Interesting. Then we have (a) predicate symbols(b) predicates (c) functions, and a predicate can be represented by a function. Eg
- 'F' is a predicate symbol [type (a)]
- under an intepretation it, 'F', can be associated with a predicate, egs. prime, even [type (b)]
- the prime, even and green can be represented by functions (from numbers to {t,f}
That gives us three ontological classes. On the princile of Ackhams razor, would it not be simpler to say
- under an intepretation 'F', can be associated with a predicate, egs. prime, even which are functions (from numbers to {t,f}
— Philogos (talk) 01:31, 18 June 2011 (UTC)
formal definition
[edit]The following in para formal definition do not provide formal definitions of the term predicate.
- In propositional logic, atomic formulae are called propositional variables.
- In first-order logic, an atomic formula consists of a predicate symbol applied to an appropriate number of terms.
The article is about predicates not predicate symbols— Philogos (talk) 02:29, 17 June 2011 (UTC)
- Indeed. — Carl (CBM · talk) 02:39, 17 June 2011 (UTC)
- So the items quoted do not provide a formal definition of the term predicate. (not to be conmsuded with the term predicate symbol or predicate letter
"atomic formula and an atomic sentence" ??? I was reading the article, and it was reasonable to follow, until I came across mention of "atomic formula and an atomic sentence". I've no idea what these are. No clue is given. What is this going on about? — Preceding unsigned comment added by 109.145.82.159 (talk) 10:46, 19 August 2011 (UTC)
Cleanup needed
[edit]In its current form, the article augments rather than reduces confusion. To begin with, proposition and predicate are mixed up. Simply put, using the notation of the article, P(x) is a proposition and P is a predicate. This is the most commonly (although not universally) used terminology. The article should be cleaned up to reflect this. Boute (talk) 07:06, 19 October 2015 (UTC)
Wrong assertion at "Simplified overview" section
[edit]- RIGHT. If t is an element of the set {x | P(x)}, then the statement P(t) is true.
- WRONG. Here, P(x) is referred to as the predicate, and x the subject of the proposition.
The x variable is not the subject (supposing a context of subject–predicate–object). See this example:
- A = {x | the square is a subclass of x} and see the set of elements here. So, the set A was defined by the use of x as object not as subject of the phrase (the predicate of the set),
- A = {rectangle, rhombus, hypercube, cross-polytope, ...}
P(x) is a template function, as in "Hello %!"
where the symbol %
is a placeholder to be replaced to anything. Correcting the WRONG to RIGHT:
- RIGHT. Here, P(x) is referred to as the predicate, and x the placeholder of the proposition.
Sometimes, P(x) is also called a (template in the role of) propositional function, as each choice of the placeholder x produces a proposition.