In Examples (67)and (69), positive and negative modal adjectives (i.e.probable and improbable)are used respectively.They are about the state of affairs and should be explicit in modal orientation.In contrast, in Examples (68)and (70), positive and negative MAs (i.e.probably and improbably)are used respectively.They are about personal attitudes, and cannot occur in questions and negations.In this sense they are implicit in modal orientation.
SFL also shows that MVs can be classified in value.Halliday (1994)does not give a clear definition of what value is.However, through his theoretical expounding and exemplification, it can be known that value is the indication of the certainty of speech or the imposition of the speaker’s will.MVs and MAs have a scale of values: high, median and low, listed in Tables 2.7.
Table 2.7 Values of MVs and MAs(after Halliday & Matthiessen, 2004: 620-622)
(NB: √ indicates the presence of a certain value, and × the absence of a certain value)
MVs and MAshighmedianlow
must, ought to, need, has to; certainly, definitely, no way, always, never√××
will, would, shall, should; probably, usually×√×
may, might, can, could; possibly, perhaps, maybe, hardly, sometimes, occasionally, seldom, rarely××√
It could be found from Table 2.7 that MVs and MAs have relatively stable modal values.For instance, may is low-valued whereas must is high-valued; maybe is low-valued whereas certainly is high-valued.
Consider the following examples (Halliday & Matthiessen, 2004: 148):
(71)That must be true.(certain)(high value)
(72)That will be true.(probable)(median value)
(73)That may be true.(possible)(low value)
Clearly, Examples (71)-(73)indicate that there is basically a steady value for each MV.However, this does not mean that it is fixed.SFL also states that the values of modal devices, especially MVs, may be changed when negated.For instance, can is a low-valued MV, but can’t is a high-valued one.Halliday (1994: 76)gives the following classification (Table 2.8)as evidence.
Table 2.8 Values of modal devices (after Halliday, 1994: 76)
lowmedianhigh
positivecan, may, could, sometimes, possiblywill, would, should, usually, probablymust, ought to, need, has/had to, always, certainly
negativeneedn’t, doesn’t have towon’t, wouldn’t, shouldn’tmustn’t, oughtn’t to, can’t, mightn’t, hasn’t to
2.1.6.2 The mood structure
SFL regards MVs as finite, which forms part of the mood structure together with subject in clause as exchange.According to Halliday (1994: 75), finite has the function of making the proposition finite, or it relates the proposition to its context in the speech event.Halliday (ibid)notes that this can be done in one of two ways.One is by reference to the time of speaking; the other is by reference to the judgment of the speaker.Modality means the speaker’s judgment of the probabilities, or the obligations, involved in what he is saying.A basic analysis of clause as exchange is exemplified in the following way:
(74)Shecan come here tomorrow.
In Example (74), the MV can is finite in the mood structure.This MV plays an important role in exchange, i.e.the interpersonal metafunction.
2.1.6.3 The system of modal adjuncts
In SFL, MAs are termed as modal adjuncts.Halliday & Matthiessen (2004: 126)divide modal adjuncts into two subcategories: mood and comment, and diagrams the relationship as in Figure 2.9.
Figure 2.9 System of modal adjuncts (after Halliday & Matthiessen, 2004: 126)
SFL makes a detailed exploration of modal adjuncts.Take mood adjuncts of temporality for example.Adverbs serving as mood adjuncts of temporality can be divided into “future” and “non-future” (past/present)ones.For either of them, there are “remote” and “near” subcategories.Eventually is future and remote, once past and remote, soon future and near, and just present and near.SFL seems to agree that adverbs that can function modally cover more than other linguistic schools think they do.In SFL, modally-oriented adverbs are not just disjuncts, but include some adjuncts and subjuncts as well.
Martin et al.(1997: 70)compare modal adjuncts and their paraphrases of projection.They argue that MAs (appearing as modal adjuncts)are the congruent realizations of modality whereas their projections (also appearing as modal adjuncts)the metaphorical realizations.Therefore, the following equations can be derived: possibly = it is possible, probably = it is probable/I guess, certainly = it is certain/I think (I know), sometimes = it is unusual, necessarily = it is necessary (it is expected)/I expect.Like Halliday & Matthiessen (2004: 626-630), Eggins (2004:174-176)indicates that the clauses as metaphorical realizations of MAs function as adjuncts like their congruent forms of MAs.For instance, the tag test can be applied to see if it is so:
(75)Henry James probably wrote The Bostonians.
(76)I reckon Henry James wrote the Bostonians.
(77)Henry James wrote the Bostonians, didn’t he?
The tag question for both the congruent form of MA in Example (75)and its metaphorical one in Example (76)is the same: didn’t he (in Example (77)).
2.1.6.4 Text types
Some scholars have studied modality in relation to text types or genres.They indicate that the use of modal devices is closely related to text types or genres.
Through the statistics of large corpora, Biber et al.(1999: 486-490)discover that on average can, will and would are extremely common while shall is relatively rare in all types of texts.They give some specific findings as proofs, such as: (i)may is extremely common in academic prose, but rare in conversation; (ii)could is particularly common in fiction; (iii)will is extremely common in conversation and news reportage.