逻辑学中的视图

Kripke states that the basic problem for accounts of naming like Mill’s “is how we can determine what the referent of a name, as used by a given speaker, is” (Kripke 28). On Mill’s view, names lack any descriptive component, and without such a component we cannot uniquely identify the referent of a name. Kripke goes on to present two arguments he calls subsidiary, but which constitute more positive reasons for favoring Russell’s view. The first is the case of two names for the same referent; on Mill’s view we should be able to use two names for the same thing interchangeably. Yet Russell’s view presents a strong case that we cannot use them interchangeably, and therefore there must be more to a name than that which it denotes. A good example of this is Hesperus and Phosphorous. Astronomers saw a heavenly body in the morning (incidentally the body that we know today to be Venus) and called it Hesperus, and saw what they believed to be a different heavenly body in the evening and called it Phosphorous. Later, the empirical discovery was made that the two heavenly bodies were one and the same. This discovery can be expressed by “Hesperus is Phosphorous.” Yet on a non-descriptive view of names, such as Mill’s, an utterance such as this has to be trivial. If both “Hesperus” and “Phosphorous” are nothing more than that which they denote, and they both denote the same thing (Venus), then the statement “Hesperus is Phosphorous” is just as trivial as “Hesperus is Hesperus.” Yet with the statement “Hesperus is Phosphorous,” “we’re certainly not just saying of an object that it’s identical with itself. This is something that we’ve discovered” (Kripke 29). We are really saying something closer to: “the heavenly body that we saw in the morning is the heavenly body that we saw in the evening.” Russell’s view that names are descriptions allows “Hesperus is Phosphorous” to be informative in this way.

Kripke’s final argument that Russell’s view is better than Mill’s is that it allows us to more accurately question whether historical figures existed. In asking whether Aristotle existed, to use Kripke’s example, we are presumably generally not questioning the existence of a flesh-and-blood man called Aristotle, but rather the existence of “anything [that] answers to the properties we associate with the name” (Kripke 29). This is dubiously phrased, as we sometimes do indeed wish to question the existence of the thing denoted, but it is true that only Russell’s view accounts for cases where we are really questioning the properties of the referent. With Aristotle, it allows us to question “whether any one Greek philosopher produced certain works, or at least a suitable number of them” (Kripke 29). This final aside alludes to what Kripke calls the “cluster view,” a modified version of Russell’s view that holds that names are really a cluster of descriptions, which must be disjunctively satisfied. I will touch on this view later. It seems clear that Russell’s view, that names are really descriptions, is thus far the best account of names as we use them.

Kripke is tactful, however, and though he constructs a strong argument for Russell, he ultimately builds him up only as a strawman to knock down. His most compelling case against Russell’s view is the following: on Russell’s view, statements such as “Aristotle was the man who taught Alexander the Great” are tautological because Aristotle is synonymous with the description “the man who taught Alexander the Great.” But the sentence in question clearly is not a mere tautology. “It expresses the fact that Aristotle taught Alexander the Great, something we could discover to be false. So, being the teacher of Alexander the Great cannot be part of [the sense of] the name” (Kripke 30). If we want statements like this to express information that could turn out to not be the case, then Russell’s view must be rejected. Kripke provides other problems for Russell’s account as well, one of which he uses to introduce his own view of names as rigid designators. Kripke gives an example in which a name’s description fails to account for essence. “What’s the difference,” he asks, “between asking whether it’s necessary that 9 is greater than 7 or whether it’s necessary that the number of planets is greater than 7? Why does one show anything more about essence than the other?” (Kripke 48).  The difference, he continues, lies in the fact that the number of planets could have been different than it in fact is, but nine could not have been any different than it in fact is. (Kripke 48). In this example, nine is a rigid designator, while “the number of planets” is not. Succinctly: we “call something a rigid designator if in every possible world it designates the same object” (Kripke 48). A name functions as a rigid designator only after it has come to designate something. We take a contingent property of an object; in the case of Nixon, e.g., that he was the president of the United States, and we use it to fix the referent of the term “Nixon,” which then functions as a rigid designator. Even though the referent is fixed by a contingent property, “Nixon” still denotes the same man even in possible worlds where he is not the president of the United States. So goes Kripke’s view.