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2012-04-07
What's the difference between the propositions 'P' and 'P is true'?
Hello

Please could someone help me with the above question.

For example, is there a difference between the propositions:

Edinburgh is the capital of Scotland.

and 

The proposition 'Edinburgh is the capital of Scotland' is true.
?

Given that the second proposition is a proposition about the first proposition, it seems to me that they can't be the same proposition.

Derrick

2012-04-07
What's the difference between the propositions 'P' and 'P is true'?
If 'P' and 'P is true' are indeed distinct propositions, then they at least directly imply each other - is there a term for a pair of propositions that directly imply each other?

2012-04-09
What's the difference between the propositions 'P' and 'P is true'?
Very likely you will not get a response to your questions because your statement of them exposes a failure to understand certain fundamental concepts and distinctions in logic and the philosophy of language.

I suggest you get a copy of Patrick Suppes' "Introduction to Logic" (Dover Publications, paperback, very inexpensive) and read chapters 1 and 6.  You might also want to get a copy of Quine's "Philosophy of Logic" (second edition, Harvard University Press) and read as much of it as you can.  At that point, either your questions will be answered or you will be able to phrase them in a way that will more likely elicit helpful responses.

(The questions that you are asking are ones the answers to which are typically covered in introductory logic, semantics, or philosophy of language courses, but whose "answers" are too lengthy to attempt in a forum of this sort.)

2012-04-09
What's the difference between the propositions 'P' and 'P is true'?
If instead of saying, "Edinburgh is the capital of Scotland," you chose to say, "It is true that Edinburgh is the capital of Scotland," the "It is true that" would be redundant.

However, your sentence "The proposition 'Edinburgh is the capital of Scotland' is true" is not the same as "It is true that Edinburgh is the capital of Scotland."

"Edinburgh is the capital of Scotland" and "It is true that Edinburgh is the capital of Scotland" are statements about the world, and the relationship that holds between the two statements is one of identity; they are the same statement.

"The proposition 'Edinburgh is the capital of Scotland' is true," on the other hand, is a different statement. It is a statement not about the world but about the proposition "Edinburgh is the capital of Scotland."

The relationship that holds between the two statements, "Edinburgh is the capital of Scotland" and "The proposition 'Edinburgh is the capital of Scotland' is true" is one of necessity. If one is true, the other is true, in all possible worlds.

This all gets a lot more complicated. Do a search on deflationary and prosentential theories of truth for more info.

2012-04-09
What's the difference between the propositions 'P' and 'P is true'?
First, your second sentence should be:
 The proposition expressed by "Edinburgh is the capital of Scotland" is true.


Let's change your example to simplify matters:


(i)      2+2=4
(ii)     The proposition expressed by "2+2=4" is true.


(i) is a necessary truth. 
(ii) is a contingent truth about a sentence in a certain notational system.


OR 


It is necessarily true that 2+2=4.
But, it is contingently true that "2+2=4" expresses a necessary truth.


Cheers,
Karl Pfeifer

2012-04-09
What's the difference between the propositions 'P' and 'P is true'?
Reply to Karl Pfeifer
Thanks, Karl. That's great. But this depends, of course, on whether we mean by "proposition" with the quote marks a) any one of a set of strings of symbols that has this particular content or meaning or b) this set of symbols, in some notational system, right?

2012-04-16
What's the difference between the propositions 'P' and 'P is true'?
Reply to Gary Merrill
Sorry about your answer, Gary. Do you really think that with conventional orthodoxy everything is done, and that  contemporary discussions, beginning with Austin's two essays, cannot tell us anything?

2012-04-16
What's the difference between the propositions 'P' and 'P is true'?
Reply to Ezra Heymann
I think that conventional orthodoxy (if I understand what you mean by that) goes a long way towards understanding basic concepts and problems.  That's how it got to be conventional orthodoxy, after all.

I think, when I see a question phrased in a manner that it makes a fundamental misuse of quotation marks (and hence commits an elementary use/mention error), that the questioner may or may not have a coherent question in mind and that, with some basic care and the use of conventions that we all accept, he or she may then actually be able to express that question so that others can understand it -- and indeed share an understanding of it.  Then the question may actually be addressed with some degree of intelligibility -- whether by "conventional orthodoxy" or other means.

I can't seem to see exactly to which Austin you intend to refer, nor to which two essays.  If it is J. L. Austin (rather, say, than my friend David), then I would have to say that it has been a very long time since I looked at Austin, but I was quite enamored with him as an undergraduate (though I later decided that his insights were neither as precise nor as generalizable as I preferred -- but don't mistake me; he was a good philosopher).  However, I don't recall J. L. Austin's ever being anxious to make simple use/mention mistakes, and I believe that he was quite well trained in conventional orthodoxy as well.  And I don't think that either he or my friend David would commit the sort of fundamental error exhibited in the original question.

That's what I think -- and what I don't think -- about this.  But perhaps you mean another Austin since you refer to "contemporary discussions" and Austin is hardly contemporary at this point.  Nonetheless, I do hold that the avoidance of fundamental error in the pursuit of asking a clear question is something that we should all value.  My original response was intended to point the questioner in that direction.

2012-04-16
What's the difference between the propositions 'P' and 'P is true'?
The relationship that holds between the two statements, "Edinburgh is the capital of Scotland" and "The proposition 'Edinburgh is the capital of Scotland' is true" is one of necessity. If one is true, the other is true, in all possible worlds.

Not if there aren't any propositions (or there are propositions in some worlds but not others), at least under most (?) theories of definite descriptions.  Also, not in full generality since a given language might lack a quotation mechanism (or might even lack a mechanism for referring to propositions even if they exist).  I'm just trying to break through the bounds of conventional orthodoxy here.  :-)

(Sorry.  I think this whole thread is fruitless since I strongly suspect it's based on the faulty assumption that the original poster was asking one particular intelligible question or other.  But I couldn't resist this.)

2012-04-16
What's the difference between the propositions 'P' and 'P is true'?
Hey, has anyone else noticed this:  http://forums.philosophyforums.com/threads/is-there-a-diff-between-the-propositions-p-and-p-is-true-53129.html?

A lot of interesting analyses there.  I think they've got the whole thing well in hand.  They also explore a number of related issues.  I particularly like the one that includes "Mathematical logic cannot handle semantic problems period.  Aristotle has showed this."

But I have to go play my tuba now.

2012-04-22
What's the difference between the propositions 'P' and 'P is true'?
Thanks very much for all your responses, which have been extremely useful. :-)

2012-04-22
What's the difference between the propositions 'P' and 'P is true'?
Dear Derrick Farnell,
The problem lies in the definition of "proposition" itself, which is often substituted with "sentence" or "(truth) statement".
The key question from which discrepancies arise lies in ontology. It is relevant if we believe that a proposition has ontological quality in the sense of speech act. This means that things come into being due to being named or claimed.

A further dificulty you find in the distinction between meaning and truth. Classical logic claims the unambigous identity of truth. This means that two statements cannot contradict each other and claim to be true at the same time. One of them must be false. Paraconsistent logic as applied in linguistics, artifial intelligence and some modern mathematics opposes this idea.

Taking your example:

Sentence 1 (S1): Edinburgh is the capital of Scotland.

If every proposition is at the same true than:

S2: Edinburgh is a northern suburb of Adelaide, South Australia.

and
S3: Edinburgh is a town between Indianapolis and Louisville, Indiana, United States.

Would be completly wrong.
In fact, as far as I know, there are at least three geographic locations on earth called Edinburgh (and spelled exactly in that way).

S1 is wrong if we understand the verbal part of speech ("is") as categorically defining, i.e. all objects called Edinburgh are capitals AND are in Scotland.
S1 could be right if we consider the verbal part inclusive, not categorical but as an example. Than you may think something like: "Edinburgh is a denomination for a geographic location (e.g. as opposed to human or animal names or movable objects). One example of Edingburgh is in Scotland, there it is a capital.

What is missing is further determinator. But it natural speech it would never solve problem. If you really want to define something in a completly unambigous way you end up with a kind monadims. Speech actually lives from ambiguity. This is why I oppose the comparision of language with classical logic and Newtonian mathematics and promote its implict requirement of praxis (usage in a concrete context).

For futher studies on this broad topic, please look up the Stanford Encyclopedia on paraconsistent logic: http://plato.stanford.edu/entries/logic-paraconsistent/

I hope, this was helpful.
Best.
Tabea Hirzel



2012-05-07
What's the difference between the propositions 'P' and 'P is true'?
Reply to Gary Merrill
I gotta agree with you on that. There are definitely a lot of interesting analyses. 

2012-09-24
What's the difference between the propositions 'P' and 'P is true'?
In case of any proposition as you say 'P', it has two truth- values - true and false. So a proposition(here in your example 'P') can be true or false. But in the second part 'P' is true, it is about the proposition 'P' and it asserts that the proposition is a true one.You are correct that they are not the same proposition. one is i.e,'P' is the proposition and the second one is 'P'is true is about the truth-value of the the proposition 'P'. Narayan  

2013-04-11
What's the difference between the propositions 'P' and 'P is true'?
Hi All!
This place looks like heaven!
Well... we will see about that shall we?

1  Let propositions not about propositions be first class
2  Let propositions about first class propositions be second class
3  Let propositions about second class propositions be third class

4 ...And so on...

5  Assumption: No proposition belong to two consecutive classes.

6 Obviously no first class proposition can be second class and your example sentence:
"Edinburgh is the capital of Scotland." seems to be first class.
Which should settle your question, but in all other cases the assumption seems false:

7 If a sentence like "This sentence uses english terms" belong to any class then it seems also to belong to next higher class since sentence 8 have the same sense as sentence 10

8 Sentence  8 use english terms. 

9 Sentence 8 = "Sentence  8 uses english terms."

10 "Sentence  8 uses english terms."uses english terms

11 If sentence P belongs to a class, then "P is true" belongs to next class, but that is not an argument showing they have not the same sense (being sentenses expressing the same statement). 

12 Definition of truth: P is true if and only if P. Which shows them to have the same sense.

13 :  P = "P is true"