Monday, May 24, 2010

Lewis, "General Semantics" II: Semantic Values for Nondeclarative Sentences

Lewis contrasts two ways of making sense of the content of nondeclarative speech acts. The two camps are (i) the "sentence radical" view, and (ii) the "paraphrased performative" view.

(i) The Sentence Radical view postulates that an uninflected declarative sentence like "you be late" is a sentence radical which is concatenated a text-scope with a mood-node: this mood-node can be declarative, imperative, interrogative, etc. The sentence radical is not itself a declarative sentence; and "fundamentally...the entire apparatus of referential semantics...pertains to sentence radicals and constituents thereof" (56). To account for moods--not a part of referential semantics, mind you--the quoted philosopher, Stenius 1967, makes reference to what sound like constitutive speech-act rules, like "(declaratively) assert s, with meaning p, iff you believe that p is true."

Lewis notes that the Sentence Radical view will have trouble with any speech act that appears not to have a complete sentence-radical as a constituent; his example is "Hurrah for Porky!"

(ii) Lewis's own view, the performative view, is advertised as having a simpler interface with `referential' semantics [I guess that would be: the semantics of the interpretation function]. We consider a complicated transformational component of the grammar which paraphrases LFs of basically this form:

[.S
[.I
]
[.VP
[.ask/command/declare
]
[.V-bar
[.you
]
[.S*
]
]
]
]

...where S* is the sentence that referential semantics tells us about. Such a transformational component would equate e.g.

I command you to be late.

with

Be late!

Thus "I [Lewis] propose that there is no difference in kind between the meanings of these performaives and non-declaratives and the meanings of the ordinary declarative sentences considered previously" (57).

NB that while Lewis appears to have the same problem as Stenius, he paraphrases "Hurrah for Porky!" as "I cheer Porky."

NB also that Lewis then assigns truth-values to non-declaratives like "Hooray for Porky" and "What time is it?" They are true, because (assuming appropriate felicity conditions) the speaker does thereby succeed in cheering for Porky and asking what time it is. Thus we must keep in mind two uses (rather than two senses) of e.g. "I command you to be late": one use is imperative, while the other is descriptive. Only the former use permits of the paraphrase "Be late!" (Which is odd, because the associated transformation is syntactic.*)

This seems like an unintuitive view (even if Stenius's is too). Why prefer it? Lewis notes that "On the method of sentence radicals, the difference between the performative and self-descriptive uses of performative sentences must be treated as a difference of meaning" (61). But this doesn't seem right to him. He compares this two the two sentences

(1) I am talking in trochaic hexameter.
(2) In hexameter trochaic am I talking.

We would want to say that the sentence have the same meaning, even though they have different available uses: "whether a sentence can be used to talk in trochaic hexameter is not a matter of its meaning" (60). Note that this example provides an interesting riposte to the asterisk-ed complaint above. It is obviously a (series of) syntactic operation(s) that account for the inter-derivability of (1) and (2). While the syntactic operations have no effect on the semantic content of the sentence, they have nonequivalent results for the usability profile of the outputs: in particular, (2) can be used to performatively, while (1) cannot. (Note strangely, then, that (1) may be false and (2) may be true at a context even if everything is held fixed prior to the utterance. Lewis will say that the difference in truth is a result of taking (2) to be used performatively, while (1) cannot be used performatively.)

****

"Index, Context, Content" revisited
...in search of disagreements between that article and "General Semantics"...

...This is found only on the issue of constant-but-complicated vs. variable-but-simple semantic values. Lewis writes that in "General Semantics," he went for the constant-but-complicated.

The difference is elusive to me. (And to Lewis, in the sense that he finds the distinction to be an unimportant one!). Lewis writes:

"...[considerations about the objects of the attitudes] does not mean that we need to equate the propositional content and the semantic value of a sentence in context. It is enough that the assignment of semantic values should somehow determine the assignment of propositional content. And it does, whether we opt for variable-but-simple values or for constant-but-complicated ones. Either way, we have the relation: sentence s is true at context c at index i. From that we can define the propositional content of a sentence s in context c as that proposition which is true at world w iff s is true at c at the index i^w_c that results if we take the index i_c of the context c and shift its world coordinate to w.

...It would be a convenience, nothing more, if we could take the propositional content of a sentence in context as its semantic value. But we cannot. The propositional contents of sentences do not obey the compositional principle, therefore they are not semantic values. Such are the ways of shiftiness that the propositional content of `Somewhere the sun is shining' in a context c is not determined by the content in c of the constituent sentence `The sun is shining.' For an adequate treatment of shiftiness we need not just world-dependence but index-dependence--dependence on all the shiftable features of context. World is not the only shiftable feature." (38-39)

(I remember being terribly confused by this passage, especially the unhelpful "such are the ways of shiftiness that...") The argument here is that we cannot take propositions to be the semantic value of sentences because sentences can embed in operators that shift indices other than the world parameter; the operator "somewhere: ..." is a case in point. The argument would also work with operators like "strictly speaking:...", "it was: ..." and the imaginary "as for you: ...".

This is a polemic against propositions as semantic values, though, which is only a special case of the variable-but-simple semantic value camp.

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