The Argument from Linguistics

Most arguments in the literature in favour of relative modality of some form are to be found in linguistics and philosophy of language, regarding the nature of modal terms. The main argument comes from the plethora of different modals of the same force, i.e. different “must”s and “can”s. There is such a great variety of modals to be found in the linguistic data, that it is implausible to think they are different words with different meanings (such that words like “must” are ambiguous in a similar way to the ambiguity of “bank”). Furthermore, all these different “must”s and “can”s do seem to share some significant portion of meaning. It makes better sense to assume that, rather than ambiguous words with many meanings, we have univocal words with one meaning along with something like parameters to be de- termined by context. Lycan (1994) motivates the view by considering the many different and subtle changes in modals in everyday use, concluding

My purpose is only to indicate that everyday English is shot through with restricted alethic modalities whose restrictions are almost capriciously diverse, rarely aligned with any easily specifi- able modal concept known to logicians, and irreparably vague— yet calculated on the spot by ordinary human speakers/hearers with hardly a conscious thought. (1994, p. 176)

Having considered this kind of data, Kratzer (1977) argues

All this leaves us with many different ‘must’s and ‘can’s. What can we do with them? We could give them different names. Numbers have been proposed. Let’s have

‘must1’, ‘must2’, ‘must3’,. . .

‘can1’, ‘can2’, ‘can3’,. . .

But we might not have enough numbers. How many bits of knowledge are there, to which we can refer? How often does the

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This might result in a kind of Modal Pluralism. However, this might undermine the Argument from Similarity, see section 1.3.2.

Queen change her mind? . . . How many kinds of duties can we take into consideration? And even if we had enough numbers, it would not be very sensible to use them here. In everyday conversation we do not use subscripts when we use the words ‘must’ and ‘can’. Somehow we do without them. And even quite easily. There must be another way by means of which we make ourselves understood using these words. (Kratzer, 1977, pp. 339-40)

For Kratzer, the explanation of this other way is a common core of mean- ing—“must-in-view-of”, “can-in-view-of”—relativized to different parame- ters. Lewis (1979) also appears to be convinced by this kind of argument.

The “can” and “must” of ordinary language . . . usually . . . ex- press various relative modalities. . . . That suggests that “can” and “must” are ambiguous. But on that hypothesis, as Kratzer has convincingly argued, the alleged senses are altogether too numerous. We do better to think of our modal verbs as unam- biguous but relative. (Lewis, 1979, p. 354)

This may be a widely accepted view regarding modal terms, but these are arguments concerning pieces of language, and the current project is concerned with the metaphysics of modality. Conclusions regarding how modal language works do not immediately tell us how reality is. However, two arguments for a metaphysical thesis of relative modality—that most kinds of modality are in fact merely relative forms of another, fundamental, kind of modality—can be formulated on the basis of arguments concerning modal language.

The first argument is an appeal to take the account of modal language seriously as a guide to modal reality. If we speak about a plentiful variety of kinds of modality, and we say something true, then we should be prepared to accept that there are many such kinds of modality in the world. And, if we take seriously the claim that our modal terms are univocal but relative, this suggests that we ought to take seriously the idea that there is one core type of modality, to which the others are relative.

One problem with this kind of argument, given my agenda, is that when it comes to giving a semantics for modal terms, possible worlds are often brought onto the scene. If one can be persuaded to take this semantics seriously, then it looks like one will have to admit a possible worlds ontology. This is what I don’t want to do. However, not all treatments of modal language use possible worlds. E.g., the semantics that Kratzer offers is situated firmly in a possible worlds framework (see Kratzer (1977, 2008)). However, Wertheimer (1972) provides an example of a treatment of modal language in other terms, namely, in terms of “Systems”, where a System is ‘a more or less well organized and integrated system of laws (and perhaps

other propositions as well) concerning some more or less well-defined set of objects’ (1972, p. 88), and “must” and “can” are analyzed in terms of contraints imposed by these Systems. Without going into detail, suffice it to say that although different linguists and philosophers disgree on the details of the semantics, there does appear to be significant consensus regarding the relativity of modals. This is the lesson we should take seriously. Where linguists and philosophers of language have converged on the relativity of modal terms, but not a specific semantics, we can take seriously the relativity without having to take on board a specific semantic treatment. We can then take this major point of agreement as a significant motivation for taking the relativity of modal language to be a reflection of the relativity of modal reality (assuming that modal language is somehow fact-stating).

Consider things from another direction. Suppose we agree that modal terms are univocal but relative, and that modal language is in the business of stating facts. If we also claim that in reality different kinds of modality are not relative to one fundamental kind, but independent, then it seems that we will have to say something like: for each (or most) relativization(s) of a modal term in our language, there is a kind of modality in the world corresponding to it, but which is not itself relative in the manner described. This seems strange. Apart from anything, why would we use the same word, with a constant meaning, to refer to so many different things? If, e.g., the “must”s in ‘2 + 2 must equal 4’ and ‘Every effect must have a cause’ denote genuinely distinct and unrelated modalities in the world, how can we explain using the same word with the same core meaning? Indeed, what could that core meaning be, if not a basic kind of modality?

One might object here that there is a significant disanalogy between the linguistic case and the metaphysical case: the linguistic accounts claim that there is a common core to all modal terms with a parameter to be fixed, whereas the metaphysical account argues that there is a fundamental kind of modality, to which other kinds of modality are relative. E.g., the core ele- ment “must-in-view-of x” is supposed to be common to logical necessity and physical necessity alike, in both cases being fleshed-out with a specification of the conditions in view of which something is necessary. In contrast, the metaphysical view takes, e.g., physical necessity to be a form of logical ne- cessity, relative to some conditions. Doesn’t this disanalogy make it difficult to use the linguistic considerations as an aid to the metaphysical view? No. Consider, there must be some kind of limiting case for “must-in-view-of”, where the set of conditions in view of which something is necessary is min- imal, perhaps empty. What kind of modality might this express? Surely a kind of necessity which is relative to no conditions is not properly described as relative at all. It seems to me that this limiting case of necessity on the linguistic view corresponds to the fundamental necessity on the metaphysical view, to which other kinds of necessity are relative.