In last week’s post I discussed some standard objections to David Lewis’ theory of Extreme Modal Realism. This week I will be assessing a different theory of modality – the Linguistic View (or the LV, for short).
The LV makes two fundamental claims: (1) modal properties such as possibility, impossibility and necessity are characteristics of the sentences expressed in a language; and (2) possible worlds are maximal sets of compossible sentences, i.e. sentences which are consistent with each other.
Claim (1) should not be confused with the idea that only uttered sentences are possible. There are many sentences expressible in the English language which have not been uttered by an actual speaker – but these sentences still have modal properties. If this were not so, the LV would “lead to the absurd conclusion that were there in fact no speakers, nothing would be possible” (Pruss, 1996, p.33).
Claim (2) about possibility depends on the notion of consistency between members of a set: sentence S is possible iff at least one internally consistent set has it as a member; S is necessary iff all internally consistent sets have S as a member or all sets that have S are internally consistent; and S is impossible iff no consistent set contains S. For example, according to the rules of the English language, a sentence like “Clinton’s U.S. presidency was inaugurated in 1993” is possible because it is a member of at least one set, though not all sets (say, those containing members like “Clinton did not swear an oath in 1993”). The sentence “Bill Clinton is a cabbage” is impossible since any set containing it would thereby have inconsistent entailments like “Bill Clinton is a human being,” “human beings are not vegetables,” and “cabbages are vegetables.” Finally, the sentence “Clinton is an entity with properties” is necessary because (as above) its denial, in any set of which it is a member, leads to inconsistent entailments.
The LV faces serious objections that make it an inadequate theory of the grounds of possibility:
First, its choice of language for constructing sets of sentences (aka. possible worlds) seems arbitrary. Why not use Cantonese or Romansh, instead of English? The LV needs to provide a non-arbitrary rationale for preferring one language above others.
Second, languages are limited to the kinds of sentences they can express. Languages have different word-meanings and are restricted to finite vocabularies and grammars for describing the world. These limitations indicate that languages do not describe every aspect of the world or any aspect of it completely. There will always be facts about the world which languages do not express, not matter how developed they become. But if (as the LV suggests) modal properties are restricted to sentences in a language, it follows that some facts about the world will not be possible simply because they are not expressed in the language we are using – and that conclusion seems counterintuitive.
Third, the LV presupposes the very notion of modality that needs explaining, because of its “requirement that we talk of maximally consistent sets of sentences” (Pruss, 1996, p.33). Saying that sentences form a consistent set amounts to saying that it is possible for each member of the set to be true. But possibility is itself a modal notion! Therefore, the LV does not account for modality.