I maintain that we must distinguish among declarative sentences, their linguistic meanings, and the propositions expressed by tokenings of declarative sentences by speakers in definite contexts. Furthermore, I maintain that propositions, not linguistic meanings, are the vehicles of the truth-values. Here are four declarative sentences in four different languages, English, German, Turkish, and Latin: I love you; Ich liebe dich; Seni seviyorum; Te amo.
Clearly, each of these sentences can be used to express many different thoughts or propositions. If Jack says 'I love you' to Jill, the proposition expressed is different from the proposition expressed if Bill says 'I love you' to Hill. Since one and the same sentence type can be used to express different propositions, it follows that sentence types are distinct from propositions.
We must also distinguish between a sentence type and its linguistic meaning, the meaning it has in virtue of the conventions of the language to which the sentence type belongs. The four sentences displayed above have the same meaning. Since one and the same meaning is possessed by these four different sentence types, it follows that linguistic meanings are distinct from sentence types. It follows from the two points just made that linguistic meanings are distinct from propositions. One proof of this is that one can have a complete understanding of the linguistic meaning of a sentence without knowing any proposition that the sentence has ever expressed. Let me explain.
Suppose a Spanish speaker learning English learns that 'Mary loves Carl' means the same as 'Mary ama a Carl.' The Spanish speaker then fully understands the linguistic meaning of 'Mary loves Carl' but without needing to know any proposition, any truth or falsehood, that the English sentence has ever expressed. (See Castaneda, Thinking and Doing, p. 35) Therefore, the linguistic meaning of a declarative sentence is distinct from the proposition expressed by the sentence on some occasion of the sentence's use. Some, blinded by the nominalist fear of reification, cannot admit this obvious distinction between linguistic meaning and proposition. One nominalist writes, "In summary, the meaning of a sentence is what it says, what it says is true or false, ergo the meaning of a sentence is a 'truth bearer'." The argument is this:
1. The meaning of a sentence is what it says.
2. What a sentence says is either true or false. Therefore,
3. The meaning of a sentence is either true or false.
The argument equivocates on 'what it says.' If premise (2) is true, then what a declarative sentence says is identical to the proposition it expresses. It is important to realize that I am not assuming any particular theory of propositions. Thus I am not assuming that they are Platonic entities. I am simply insisting that we need to distinguish between the linguistic meaning of a sentence (the meaning it has in virtue of the conventions of the language to which it belongs) and the proposition a sentence expresses when the sentence is uttered or otherwise tokened by a person in a definite situation. But in premise (1), the linguistic meaning of a sentence is identified with what it says. Thus 'what it says' is being used in two different ways, which fact destroys the validity of the argument. If a proponent of the argument says I am begging the question against him, I reply that he is failing to admit an obvious distinction. The distinction is not original with me. It ought to be visible to anyone. If an a priori commitment to nominalism blinds one to so obvious a distinction, then so much the worse for an a priori commitment to nominalism.
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