Using Sweetser’s theory a big number of MV usages may be explained.For example:
(34）I can lift fifty pounds.
“Some potentiality enables me to lift 50 lbs.”
(35）You can’t have lifted fifty pounds.
“Some set of premises disenables me from concluding that you lifted 50 lbs.”
(36）He has to be home by ten.
“Some force of authority compels him to be home by ten.”
(37）He has to be a New Yorker, with that accent.
“The available premises, including his accent, compel me to conclude he’s from New York.”
Sweetser’s theory is attributed to Talmy (1988）in which the original insight is that MVs are best analyzed in terms of force dynamics.Sweetser (1990）greatly expands Talmy’s insight, arguing that force-dynamic values are applicable either to the domain of social interaction or to the domain of reasoning, and that this difference in domain accounts for the contrast between the root and epistemic senses.Boye (2005: 61）argues that the force dynamics of modality can be staged as follows in Figure 2.2.
According to Figure 2.2, the agonist as the recipient of action (agonist）changes gradually from the passive role to the active one, and in this process modality changes from obvious to covert in terms of modal source.This is a further support to Sweetser’s idea; however, Boye’s model of the force-dynamic situation is applicable to root modality (including deontic and dynamic modality）only instead of both root and epistemic modality.
Partly supporting Talmy and Sweetser’s view, Langacker (1991）prefers to explain the force-dynamic values of MVs by means of the Dynamic Evolutionary Model.In his view, the speaker is involved as the primary conceptualizer and the person responsible for assessing the likelihood of reality evolving in a certain way.When the speaker conceives of how the world is structured and how reality is currently developing, his activity can be thought of as the weighting of evidence.When that conception is used as a basis for extrapolation, projecting the future evolution of reality, the mental path is thought of as a deductive path leading from the evidence towards a possible conclusion.The deductive path is described as follows (Langacker, 1991: 275):
…a future-time modal is already quite subjective in its construal of directed potency, but it is still concerned with what might happen in the world, i.e.with reality evolving in one way rather than another.By contrast, a present-time modal pertains to a situation whose status as part of reality or non-reality has already been determined-it is just that the speaker does not yet know where it falls.Hence it is not reality, but rather the speaker’s knowledge of present reality, whose continued evolution must be assessed and projected into the future.The notion of evolutionary momentum therefore receives a more subjective construal, because it is now attributed to known reality, which lies within the province of the conceptualizer.(Italicized parts being original)
The Dynamic Evolutionary Model of MVs can be diagramed in the following way in Figure 2.3.
In Figure 2.3, C is the conceptualizer (identified as the speaker).With respect to this model as the explanations for future events or states, MVs can be described as the expressions of potential reality and projected reality respectively when the development line is unknown (or hard to predict）or known (or predictable).The Dynamic Evolutionary Model seems to work well for epistemic MVs.
As has been indicated, the force dynamics method construes modality as part of a cognitive process in which the addresser as a conceptualizer imposes a force on the addressee (s).The force can then be responsibility, permission, likelihood, order or request.Nevertheless, due to the constraints of settings or pragmatic factors, it is doubtful whether the force designated can be achieved.
2.1.4 The approach of pragmatics
The approach of pragmatics considers the use of modal devices as the means of conducting speech acts, or indicating the reliability of the sources of information.Hence, modal devices are related to social functions.Basically, there are two methods involved, namely, speech acts and evidentiality.
2.1.4.1 Speech acts
The speech act method lays emphasis on the perlocutionary effects of linguistic devices, i.e.what effects the use of a certain linguistic device would produce on the addressee.Consider the following:
(38）Can you please repair this watch?
The MV “can” in Example (38）is not treated as asking for permission or about ability.Instead, it is taken as a request for an action.Such expressions are mostly assumed to be conventional.Yet, Leech (1983: 29-30）holds a different view.According to him, such indirect requests are primarily motivated and secondarily conventional in pragmatics.Leech (1983: 37）draws a figure to explain that (as in Figure 2.4).
From Figure 2.4, it can be understood that communicative settings and purposes play an important role in construing speech acts for either side of the communication.Pragmatics, described as problem-solution by Leech (1983: 35), thus, draws much on the pragmatic inputs of the communicators, namely, the indirect speech acts conveyed by modal devices.Studies by Levinson (1983）and Brown & Levinson (1987）on direct and indirect speech acts indicated by MVs basically take the same line as Leech does.
In Figure 2.4, 1 is the initial state [Speaker wants to get his watch repaired], 2 refers to the intermediate state [Hearer understands that Speaker wants to get his watch repaired], G indicates the goal of attaining 3 [getting the watch repaired], a expresses the Speaker’s action of asking for permission or about ability, and b denotes the Hearer’s action in repairing the watch.This figure is helpful for the explanation of the role of the MV can in Example (38).