On Philosophy

October 29, 2006

Definitions II

Filed under: Language — Peter @ 1:14 am

It’s been a bit hectic around here, so instead of a “real” post I have created a concise list of definitions for terms used in the philosophy of language. I suspect most of my readers already know what they mean, but simply creating such a list means that I don’t have to define them every time I use them in the future, I can simply link here without sacrificing clarity. So without further ado:

Intension:
The intension of a word, roughly, can be thought of as what is intended by the use of a word. Obviously then intension is closely connected with sense (see below), one might even say that they were the same (I am so inclined), but it is not necessarily the case. At the very least words with the same sense have the same intension. Some, including myself, think that the intension of a word can be defined as the set of all objects that the speaker thinks that the word could reference, in all possible worlds. For example, for the word “cat” the intension would be the set of all cats in all possible worlds.

Extension
The extension of a word is commonly accepted to be the set of all objects (in this world) that the word references. For example, the extension of “cat” is the set of all cats. The classic example to demonstrate the difference between extension and intension is creature-with-a-heart and creature-with-a-kidney, which have the same extension, but not the same intension.

Sense
The sense is what determines the reference of a word (according to Frege). Of course in this context reference could be interpreted as the set that we identify with the extension, or the set we identify with the intension, or the reference, as defined below. What the sense is, exactly, is a matter of some debate. Some think that it is a mental process, which would imply that we could collapse sense and intension together (or ate least the mental acts that give a word its intension). Others, like Frege, think that the sense is itself some kind of abstract object that we enter into a cognitive relation with when we use language.

Reference
I define reference in a way that is a bit non-standard. Some authors use reference to mean essentially the set that defines the extension, or possibly the set that defines the intension. Either way the reference is objects in the world. Since we already have “extension” and “intension” I define reference slightly differently, as the object(s) in the world meant by the use of a word in some context. This won’t always be the same as the extension, although it will definitely be some subset of the extension. For example, if I use the word “lake” the reference is the lakes that exist on Earth, which are in some way connected to my use of that word. However there may be lakes on other worlds, lakes that fall under the extension of “lake” as I use it, but which aren’t the reference of my use of “lake”. Of course I don’t advocate making distinctions for their own sake, but this particular distinction is extremely useful in describing where some arguments for externalism go wrong (see here).

T theory / T sentences
A T theory is a set of rules that take sentences in some language and transform them into sentences such as “‘X’ is true if and only if Y”, which are called T sentences. Some, notably Davidson, claim that a T theory for a language captures the meaning of that language, and thus that T theories are theories of meaning.

Object Language / Metalanguage
In a T sentence such as “‘X’ is true if and only if Y” X is a sentence in the object language, while the whole statement is a sentence in the metalanguage. When T theories were originally developed by Tarski the object language was a formal mathematical language, but obviously this is not the case when applied to natural languages. The metalanguage, when dealing with natural languages may be a different natural language, or it may be “pure propositional content”, that is claims about the way the world is. Generally it is accepted that if the metalanguage and the object language are the same then the T sentence is uninformative.

Meaning / Content
I won’t even attempt to define meaning here (not that I haven’t put forward theories about it elsewhere). Currently there are basically two ways of looking about meaning. One is to identify it in some way with the intension or sense, and the other is to identify it with the reference or extension (for example, T theories seem to be identifying it with intension). Identifying meaning or content with the reference or extension seems tempting to many (especially externalists), but it does have some problems in dealing with the difference between statements such as a = a and a = b. If a and b have the same meaning, and the meaning is the reference or extension, then both statements are saying the same thing. They certainly don’t seem to be though, and thus the philosopher who wishes to identify meaning and content with the reference or extension has some work to do.

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