Friday, February 24, 2012

Maverick and Belette on Frege

Back after a software-imposed break. While all this was going on, Maverick philosopher commented on my Frege post, gently supportive but questioning whether cognitive value or informational content can be had by such subsentential items as 'morning star' and 'evening star.' I think it can be had. We both agree the proposition "grass is green" has informational content. This content differs from the content of "grass is yellow". How? How does changing the word 'green' to the word 'yellow' change the informational content of the whole proposition? Surely because the informational value of the word 'green' is different from the informational value of the word 'yellow'. Thus the informational value of a term is precisely its contribution to the informational value of the whole sentence. Frege says somewhere that the same sense corresponds to the same word, and that is why language is useful. We could use a single sign for the whole proposition, as with a train signal (red = the track is closed, green = the track is clear), but he says that would not be very helpful, as we would have to devise a new sign for every different thought we wanted to express. So we split the thought up into parts, with a different sign corresponding to each part of the thought.  If we understand 'informational value' in this way - as the contribution to the informational value of a whole proposition, my argument is sound.

Cmmenting on the post back here, Belette wondered whether my argument was valid at all. I argued as follows.

(1) The sentence “the morning star is the evening star” has informational content.
(2) The sentence “the morning star is the morning star” does not have informational content.
(3) Therefore, the term “the morning star” does not have the same informational content as “the evening star”.

Belette says that ‘the morning star’ really means ‘Venus, at certain positions in its orbit’. I’ll alter this (because I’m not sure the morning/evening distinction is anything to do with the orbit of Venus, as opposed to the rotation of the earth on its axis) to ‘Venus as it is in the morning’. Perhaps I am not understanding him, but I think he means that this expression is something that has a referent in the morning, but at no other time. As the earth rotates and Venus appears to rise in the sky and disappear in the glow of the rising sun, the reference of the expression fails, and becomes non-existent. And as the sun ‘sets’, the referent of ‘Venus as it is in the evening’ comes into existence. Thus the referent of ‘Venus as it is in the morning’ only exists in the morning, and the referent of ‘Venus as it is in the evening’ only exists in the evening. Venus, of course, exists all the time.

But if that is true, the argument above is no longer sound. The sentence “the morning star is the evening star” actually means “Venus as it is in the morning is Venus as it is in the evening”. But this is always false, for if the term on the left has a referent, it must be morning, in which case the term on the right has no referent, and the identity statement is false. Conversely, in the evening, the left term has no referent, and the right term does. Or neither term has a referent, in which case there can be no identity either (identity being a relation between existing things). Hence the second premiss is false, on the assumption that a sentence which is false in virtue of its meaning contains no information.

I question whether ‘the morning star’ does mean that. Surely it is a description picking out a certain object by means of its visibility in the morning. It is not part of its meaning that the object must cease to exist once morning has passed. It may cease to exist, of course, just as the light in the fridge ceases to exist when we shut the door. But continuation or cessation of existence is not part of its meaning. (Perhaps it is different for ‘the prime minister of England’, but that is a different case, I think).

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13 Comments:

Blogger Belette said...

> Belette says that ‘the morning star’ really means ‘Venus, at certain positions in its orbit’. I’ll alter this (because I’m not sure the morning/evening distinction is anything to do with the orbit of Venus, as opposed to the rotation of the earth on its axis) to ‘Venus as it is in the morning’.

I didn't say "it really mean that". I said (well I can't be bothered to look it up) that is *can* mean that.

What I meant by my phrasing was that whether you see Venus in the morning or evening depends on our relative orbital positions, so your rephrase is fine.

> I question whether ‘the morning star’ does mean that

I don't see how you can possibly answer that question. It will probably mean different things to different people. You could look it up in the dictionary, but that wouldn't help either.

3:06 pm  
Blogger Edward Ockham said...

I was trying to interpret what you meant, but facing grave difficulties. For example, you said "You're assuming that all objects have names that never change over time. If "the morning star" actually means "the planet Venus, when in portion X of its orbit wrt Earth"; and "the evening star" means "when in portion Y"; then MS = ES is wrong."

I don't understand how a name can 'change over time'. How can a name change?

And if you mean that Venus, when in portion X of its orbit, is not identical to the evening star, you are wrong. Given the identity, the Evening Star is always the Evening Star, even in the morning, and whatever its position.

>>I don't see how you can possibly answer that question.

I was simply saying what 'the morning star' does not mean, based on simple logic. It may be difficult to say what its meaning is, it is easier to say what its meaning is not.

3:16 pm  
Blogger Belette said...

> I don't understand how a name can 'change over time'. How can a name change?

Well, we might call Venus "stoat" at perigee, and "woat" when at apogee. Or my name might be "Mr Stoaty" before noon and "My Weaselly" after noon.

Why is a given object obliged to have the same name all the time?

6:04 pm  
Blogger Edward Ockham said...

>>Well, we might call Venus "stoat" at perigee, and "woat" when at apogee. Or my name might be "Mr Stoaty" before noon and "My Weaselly" after noon.

Why is a given object obliged to have the same name all the time?
<<

Ah you mean that an object might have a different name at different times (or indeed at the same time).

But now you are mired in a fundamental confusion. The identity statement

A = B

is not saying that the name "A" is identical to the name "B". For that would be written

"A" = "B"

Note the quotation marks. But of course one name can never be anything other than it is. By contrast

A = B

tells us that "A" and "B", though different names, are names of the same object.

7:53 pm  
Blogger Edward Ockham said...

You are also confusing a proper name with a definite description. More later.

7:54 pm  
Blogger Belette said...

I know about the difference between a pointer and the thing pointed to. I'm a software engineer. Its all a lot clearer in an artificial language; one day philosophers will realise that.

2:18 pm  
Blogger Edward Ockham said...

>>one day philosophers will realise that.

Frege said this in about 1886, Russell closely followed him. There was a whole movement in the early to mid twentieth century based on interpreting natural language using the formalities of the predicate calculus.

What are you saying that philosophers are not realising?

5:18 pm  
Blogger Belette said...

I'm saying "Its all a lot clearer in an artificial language; one day philosophers will realise that."

Its no good saying that someone has already pointed this out; philosophers need to actually realise it. Their writing, and yours, demonstrates that they haven't.

10:02 pm  
Blogger Anthony said...

FWIW, I know quite a lot about pointers and software engineering, and it's not clear to me what you're trying to say.

I do continually have a problem with Ed's frequent switch between propositions and sentences though, and I guess I could see this as a sort of dereferencing problem.

12:53 am  
Blogger Edward Ockham said...

>>I do continually have a problem with Ed's frequent switch between propositions and sentences though

By 'proposition' I nearly always mean a declarative sentence, which is the traditional usage. Sometimes I use it to mean what is asserted by a declarative sentence, i.e. to mean what the sentence says, rather than the sentence itself. It should always be pretty clear which usage is intended, in my view.

8:08 am  
Blogger Edward Ockham said...

>>I'm saying "Its all a lot clearer in an artificial language; one day philosophers will realise that."
<<

What is the 'it' that is supposed to be a lot clearer? That's what I'm not seeing.

8:30 am  
Blogger David Brightly said...

It may be worth pointing out that the difference between pointer and thing pointed at is clearer in programming languages than natural languages because the referencing model, at least in low-level programming languages like C, is essentially Direct Reference.  Two pointer variables refer to the same object iff they contain the same memory address.  So the test for co-reference is comparison of contents,and this works uniformly for all pairs of pointer variables.  An object's address behaves like a proper name and possession of the name amounts to possession of the object, just as in DR.  Natural languages are substantially more complicated.  For definite descriptions such as the brightest object around dawn and the brightest object around dusk, there is no simple test for co-reference that applies uniformly to all pairs of descriptions.   Natural objects don't have barcodes or RFID tags attached to them, so Direct Reference is ruled out.  Hence the hundreds of years between the Babylonians, who took Hesperus and Phosphorus to be distinct, and the Greek discovery of their identity.

10:41 am  
Blogger Edward Ockham said...

>>It may be worth pointing out that the difference between pointer and thing pointed at is clearer in programming languages than natural languages because the referencing model, at least in low-level programming languages like C, is essentially Direct Reference.
<<

Yes. The pointer has meaning only if at accesses the right bit of memory, otherwise it is useless. Thus meaning=reference.

4:22 pm  

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