Hunston & Francis (2000）explore the grammar of English based on corpus, and propose the concept of pattern grammar in contemporary English.According to pattern grammar, there are two principles in language use.One principle that meanings are made in chunks of language in a more-or-less predictable way is called the idiom principle.The other principle that language is seen as a result of a very large number of complex choices is called the open-choice principle.Both the idiom principle and the open-choice principle are described as ways of seeing or of interpreting language.In other words, a language user, when faced with an instance of language use, has to decide whether to interpret this as a chunk, or as a series of individual items.In some cases both principles work whereas in other cases one principle takes priority over the other.
Considered diachronically, the co-occurrence of modal devices can be the product of the idiom principle; tackled synchronically, other modal patterns are flexible, and may be the products of both principles or of a situation where the open-choice principle prevails.The use of multiple modal devices comes into being with sound diachronic and synchronic motivations.
Linguists studying modality at the typology and evolution levels by means of the functional representation approach agree that modal devices are universally common in all languages, judged from both diachronic and synchronic points of view, and they have also indicated the necessity of the co-occurrence of modal devices in discourse.
2.1.6 SFL
SFL explores modality from five aspects.They are the modality system, the mood structure, the system of modal adjuncts, text types or genres, and critical discourse analysis (hereafter CDA).Basically speaking, the use of modal devices is a matter of choices according to the interpersonal roles involved.
2.1.6.1 The modality system
SFL places modality in the part of the interpersonal metafunction, and sets up a modality system as follows in Figure 2.8.
In SFL, modal devices are put in the categories of modalization and modulation.Modalization and modulation are related to information, and goods-&-services respectively.Halliday (1994）gives a classification of modalization and modulation as follows in Table 2.4.
From Table 2.4, it can be known that there are two categories of modalization: probability and usuality.They form a paired relationship.For instance, both certainly (as a modal device of probability）and always (as a modal device of usuality）can mean “it must be”, a high-valued prediction or likelihood.Similar situation happens to modulation.For instance, both required (as a modal device of obligation）and determined (as a modal device of inclination）can mean “must do”, a high-valued obligation or will.This system applies to both MVs and MAs.
According to SFL, MVs may provide either of two speech functions: information (i.e.modalization, including probability and usuality), or goods-&-services (i.e.modulation, including obligation and inclination).Halliday (1994: 357）illustrates this classification by the following examples concerning MVs:
(62）There can’t be many candlestick-makers left.(probability)
(63）It’ll change right there in front of your eyes.(usuality)
(64）The roads should pay for themselves, like the railways.(obligation)
(65）Voters won’t pay taxes any more.(inclination)
SFL indicates that modal devices may be subjective or objective depending on the role of the speaker, and implicit or explicit depending on the way of expression.SFL gives a classification of MVs, MAs and modal adjectives according to the division between subjectivity and objectivity as in Table 2.5.
Table 2.5 indicates that MVs are subjective whereas MAs and negated modal adjectives are objective.
Consider the following:
(66）Mary will know.
Will in Example (66）is subjective and implicit, for it expresses the speaker’s prediction indirectly.
SFL presents a description of implicitness vs.explicitness of MVs, MAs, and modal adjectives.Table 2.6 is an illustration of such a modal orientation.
Table 2.6 shows that in terms of modal orientation MVs and MAs are implicit whereas negated modal adjectives are explicit.In Halliday & Matthiessen (2004: 622), negated modal adjectives are explicit modal expressions because of the transference of negation.Halliday & Matthiessen (2004: 614-615）generalize four situations for modal implicitness vs.explicitness:
A.projecting mental clause (e.g.I guess and I suppose）- explicit;
B.MVs (e.g.may and must）- implicit;
C.MAs (e.g.certainly and probably）- implicit;
D.Relational clause with factual carrier: clause and modal attribute (e.g.it is probable that…, and it isn’t possible that…）- explicit.
The view of Halliday & Matthiessen (ibid）concurs with that of Lang (1979), who points out that MAs are implicit while modal adjectives explicit in modal orientation.Lang (1979）argues that modal adjectives belong to the proposition and refer to an element of the world (the state of affairs), while MAs are not part of the propositional meaning but express a speaker’s or writer’s attitude toward the proposition (obviously, the speaker or writer cannot question or negate his/her own current attitude).Consider the following examples:
(67）Is it probable that they have run out of fuel?
(68）* Have they probably run out of fuel?
(69）It is improbable that they have run out of fuel.
(70）* Improbably they have run out of fuel.
(* indicates unacceptability)