PHILOSOPHYOFLANGUAGE语言哲学

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1、PHILOSOPHY OF LANGUAGE,HOW TO TALK ABOUT TALK,LOGICAL SEMANTICS,Remember: In logical grammar there are 5 kinds of expressions: Predicates: woman, sweet, walks Names: Fred, , Colorado Definite descriptions: the square root of 4, the King of France, the man drinking a martini Logical operators: and, o

2、r, not, if, then, any, each, some, most, at least one. The first four are called “sentential connectives,” the remaining ones are called “quantifiers.” Sentences,LOGICAL SEMANTICS,Predicates stand for classes of things. So, apple stands for the class of apples. Note Well: When I asked the class what

3、 apple stood for some people said “a fruit.” But I wasnt asking for an explanation of what apples are. I wasnt asking for a dictionary definition. I was asking what things you would point to when teaching a child to use the word apple. That would be apples, of course. Comprende? Names stand for or r

4、efer to the single things they are names of.,LOGICAL SEMANTICS,Definite descriptions also refer or stand for single objects. The F stands for the unique thing that is F, if there is one. If there isnt one, the definite description is improper. Examples Questions: Is the Rocky Mountains a name or a d

5、efinite description? Is my father a definite description? Sentences stand for truth values. So all true sentences stand for the same thing, namely, the truth. Likewise for all false sentences. So here again we see the difference between meaning and reference. Not all true sentences have the same mea

6、ning! Otherwise there would be only one true statement to make!,Sense and Reference,We have seen that there are pairs of expressions that (a) have the same reference (nominatum), but (b) do not have the same sense or meaning. More examples It was Frege who first called attention to this rather obvio

7、us fact. But if its so obvious, whats the big deal? The big deal is that such examples confirm that meaning (sense) and reference are not the same thing. In general, the meaning of a word or phrase or sentence is not the thing or things the word (etc.) stands for.,SENSE AND REFERENCE,Even though we

8、say we would teach a child the “meaning” of the word wasp by pointing out the referents-the things belonging to the class of wasps (wasps) and saying “wasp,” we do not thereby convey the meaning of the word! At least that is what Frege is committed to saying. For Frege, the meaning of any expression

9、 (logical operators aside) is one thing, its sense is another. You should think about this point carefully because later we will find that Kripke argues that Frege is wrong about words like wasp, though he is right about other expressions. (But what could be so special about wasp?) It was Frege who

10、first called attention to the importance of the sense/reference distinction.,Freges Argument,Frege didnt simply point out that there are pairs of expressions having the same reference but that differ in sense, and hence that sense and reference are not the same thing. He gave a special, rather compl

11、icated argument-one that would only occur to a philosopher/logician. But Freges argument is meant to support the position that every type of expression exhibits the sense/reference distinction. The simpler argument wont support that position. Well see why later.,FREGES ARGUMENT,“ When we found a = a

12、 and a = b to have different cognitive values the explanation is that for the purpose of knowledge, the sense of the sentence is no less relevant than its reference, its truth value. If now a = b, then indeed the reference of b is the same as that of a.,FREGES ARGUMENT CONTINUED,And hence the truth

13、value of a = b is the same as that of a = a. In spite of this the sense of b may differ from that of a, and thereby the thought expressed in a = b differs from that of a = a. In that case, the two sentences do not have the same cognitive value.”,FREGES DIALECTIC,We could try putting all this in argu

14、ment form. We uncover the conclusion and the premises (reasons supporting the conclusion) and then we evaluate the argument to see if it is any good. But I think this would miss much of the action. It will be more fun to focus on Freges dialectic: the particular way he sets up the problem and deals

15、with it. Frege focuses first on identity statements. Why?,FREGES DIALECTIC,Examples: Creatures with a heart are (=) creatures with a kidney. Jones is (=) the murderer. the sun today is the same as (=) the sun yesterday. Question: Why does he focus on such statements? Answer: He wants to focus on exp

16、ressions having the same reference. (Why?) And two expressions a and b have the same reference just in case a = b is true!,FREGES DIALECTIC,Freges dialectic proceeds as follows: He first states a fact: Identity statements of the form a = b can differ in “cognitive value” from trivial statements of t

17、he form a = a. Frege then argues that this fact is, on the face of it, contrary to logic. He concludes that fact and logic can be reconciled by means of the sense/reference distinction.,DETAILS,About 1: By cognitive value Frege just means the value of the information conveyed. If I inform the police

18、 that Jones is the murder, I give them information they can act on. But if I tell them that the murder is the murderer, they would just laugh. About 2: But if all identity statements state the obvious-that an object is identical to itself, then how can any of them convey useful information?,DETAILS,

19、More about 2: But its obvious that not all identity statements state the obvious, since some are false. More about 2: However, if it is true that Jones is the murderer, and there is no such thing as the sense/reference distinction, then how can Jones is the murderer say anything more than that the m

20、urderer is the murderer or Jones is Jones? It cant. About 3: Therefore, we need the sense/reference distinction to explain how a = b, if true, can differ in cognitive value from a = a (or b = b). The explanation is that if a and b differ in sense, if not in reference, then a = b can convey useful in

21、formation.,OTHER SUPPORT FOR THE DOCTRINE OF SENSES,Some meaningful expressions have no reference. Predicates always refer, since even if the predicate applies to nothing,its reference will still be a set-namely, the empty set. But other expressions seem to lack reference altogether. Examples: the l

22、argest number, the present King of France, Sherlock Holmes Frege can (and does) appeal to the doctrine of sense to explain how these expressions can be used meaningfully even though they lack reference.,OTHER SUPPORT FOR THE DOCTRINE OF SENSES,2. Frege argues that the references of sentences are the

23、ir truth values. Whether this is so or not, the doctrine of senses is needed to explain why it is not true that all true (or false) sentences have the same meaning. 3. Frege can and does use the sense/reference distinction to solve the following irritating but deeper-than-you-think puzzle:,OTHER SUP

24、PORT FOR THE DOCTRINE OF SENSE,A: The Babylonians believed that the morning star is the morning star, is true. But the sentence B: The Babylonians believed that the morning star is the evening star, is false. Yet since the morning star is the evening star, logic, unsupplemented by the sense/referenc

25、e distinction, dictates that if A is true, as it is, then B should also be true. Why? Frege argues that it is precisely the fact that the morning star and the evening star differ in sense that accounts for the difference in truth value of A and B.,WHAT ARE SENSES?,Two kinds of “what are (is) so and

26、so” questions. To the first Frege would answer that senses are “modes of presentation” (of the references). The triangle example. The point of intersection of lines a and b = the point of lines b and c. Some critics have pointed out that there is some tension between this explanation and Freges view

27、 of empty terms.,WHAT ARE SENSES?,To the second type of “what is” question Frege answers as follows: “The reference of a proper name or other referring expression is the object itself which we designate by its means; the idea is wholly subjective; in between lies the sense, which is indeed no longer

28、 subjective like the idea but is yet not the object itself.” And “the idea aroused in a hearer by a word shall not be confused with its sense or reference.” The telescope example,THE REFERENCE OF SENTENCES,The Slingshot (Churchs Version) Freges Principle: Substitution of co-referring expressions pre

29、serves the reference of the whole compound expression. Example: the center of mass of the earth is the center of mass of the third planet from the sun. Frege extends this principle to compounds that are declarative sentences. Step 1. Sir Walter Scott is the author of Waverly. Step 2. Sir Walter Scot

30、t is the man who wrote 29 Waverly novels. By Freges Principle. Step 3. The number of Waverly novels Sir Walter Scott wrote is 29. Expresses the same proposition as in Step 2. Step 4. The number of counties in Utah is 29. By Freges Principle.,THREE PROBLEMS,What is the sense of an actual proper name?

31、 Freges writes: “In the case of an actual proper name such as Aristotle opinions as to the sense may differ.” Possibility: the pupil of Plato and teacher of Alexander the Great. But then if Aristotle hadnt done these things he would not have been Aristotle; and if someone else had done them instead,

32、 he would have been Aristotle! That seems completely wrong. Aristotle was Aristotle whether or not he did these things. This is one of the criticisms Kripke develops.,THREE PROBLEMS,2. In contrasting the cognitive value of a = a with that of a = b, Frege claims that the former is “analytic” and “a p

33、riori.” This just means that a = a is guaranteed to be true by pure elementary logic alone, and that it can be known to be true without any examination of the world (provided we assume a is not empty). This suggests that Frege thought that a = b, if true and informative, is never guaranteed to be tr

34、ue by logic alone and that it is never a priori. But what about mathematical identities such as 2 is the positive square root of 4. Cant we see this a priori? But its still informative. And isnt it guaranteed to be true, if not by logic, then by mathematics?,THREE PROBLEMS,3. Consider a scientific i

35、dentity statement such as water is H2O. What is Frege committed to saying about this? (a) Its informative; (b) its not analytic or a priori; (c) the words water and H2O differ in sense. Judging from what he says about proper names, Frege would probably hold that the sense of water is something like

36、“the clear liquid found in oceans, lakes, etc and . Where this may be fleshed out by descriptions of the stereotypical properties of water. On this reading the statement that water is H2O might have turned out to be false. How? But Kripke argues very effectively that if the stuff in our rivers and streams etc. had been something other than H2O, it would not have been water at all. If so, what follows as regards Freges position?,