REFERENCE: is a relationship between certain uttered expressions and things in the world.
-The sense of an expression is its relationship to semantically equivalent or semantically related expressions in the same language.
-By seeking in the context of the utterance some object to which he predicates in the referring expression apply?
The context of an utterance is a part of the universe of discourse.
In the case of expressions with constant reference, a speaker could be said to know what they refer to simply by having memorized a permanent connection in his mind between each expression and its referent. In the case of expressions with variable reference, there is no single referent with which the speaker could establish a permanent connection in his mind.
EXTENSION: of a one-place predicate is the set of all individuals to which that predicate can truthfully be applied. It is the set of things and which can potentially be referred to by using an expression whose main element is that predicate. Example:The extension of window is the set of all windows in the Universe. The extension of dog is the set of all dogs in the Universe.
In the case of most frequent common nouns, at least an extension is a set of physical objects.hus, extension contrasts with sense, since a sense is not a set of anything. And extension contrast with referent, since a referent is normally an individual thing, not a set of things.
Extension is like sense, and unlike reference, in that it is independent of any particular occasion of utterance.
*A speaker’s knowledge of the sense of a predicate provides him with an idea of its extension. For example, the ‘dictionary definition’ which the speaker accepts for cat can be used to decide what is a cat, and what is not, thus defining implicitly the set of all cats.
*The referent of a referring expression used in particular utterance is an individual member of the extension of the predicated used in the expression; the context of the utterance usually helps the hearer to identify which particular member it is.
A speaker of a language in some sense knows the extensions of the predicates in that language, and uses this knowledge to refer correctly to things in the world.
Since clearly one can refer to things which no longer exist and to things which do not yet exist, and since the notion of the extension of a predicate is defined as a set of potential referents, we are forced to postulate that extensions are relative to all times, past, present, and future.
Predicates are almost always accompanied in sentences by a marker of tense (past or present) or a future marker, such as will. These have the effect of restricting the extensions of the predicates they modify, so that, for example, the extension of the phrase is dead could be said to be the set of all things which are dead at the time of utterance.
It has tempted some philosophers to try to equate the meaning of a predicate, or combination of predicates , simply with its extension, but this suggestion will not work. This flaw can be described as the undecidability of extensions.
In practice , certain kinds of predicates present more difficulties than other. It is unusual, in everyday situations, for there to be much problem in applying the predicates. But in the case of some other kinds of predicates, it is obvious that everyday language does not put well- defined boundaries around their extensions.
The original motivation for the idea of extension was to explain the ability of speakers of a language to group entities having similar characteristics.
A PROTOTYPE of a predicate is an object which is held to be very typical of the kind of object which can be referred to by an expression containing the predicate. In other words, the prototype of a predicate can be thought of as the most typical member of the extension of a predicate.
For example, a man of medium height and average build, between 30 and 50 years old, with brownish hair, with no particulary distinctive characteristics or defects, could be a prototype of the predicate man in certain areas of the world.
You will be able to think of other examples of cultural differences leading to different prototypes.
The kind of definition by pointing is called ostensive definition. It is very plausible to believe that a child’s first concepts of many concrete terms are induced by ostensive definition involving a prototype. Obviously, however, not all concepts can be learned in this way.
Some predicates which do not have clearly defined extensions do in fact have clear prototypes, but in other cases, such as abstract mass terms, there is about as much difficulty in identifying the prototype of a predicate as there is of identifying its extension.
The REFERENT of a referring expression is the thing picked out by the use of that expression on a particular occasion of utterance.
The EXTENSION of a predicate is the complete set of all things which could potentially be the referent of a referring expression whose head constituent is that predicate.
A PROTOTYPE of a predicate is a typical member of its extension.
We make a distinction between between prototype and stereotype. In other texts, the two terms are often used interchangeably. In many cases denotation can be thought of as equivalent to extension. Thus, for example, the predicate cat can be said to denote the set of all cats. But often the term is used in a wider, essentially vaguer, sense, especially problematical.