English grammar - Roger Berry 2012
B6.5 Conclusion
B6 Modal auxiliaries
Section B Development
The meanings and uses of the modal auxiliaries are not easy to capture. This is partly because there is no one-to-one correspondence between form and function (or meaning). One meaning may be expressed by more than one modal (though sometimes with slight differences, such as in formality), and one modal may express several meanings. It is certainly wrong to match one modal with one meaning, e.g. can with ability. And it is unhelpful to claim, as some grammars and textbooks do, that the modals exhibit present and past tenses in the same way that verbs do.
But the problem is also that the modals are bound up with interpersonal ideas of tentativity and politeness, with functions such as making suggestions and requests (Can you turn it down?), directing people to do things (You will do it), and so on, in addition to merely moderating the factuality of events. This is particularly true in academic communication, where speakers and writers not only want to express lack of certainty with the use of modality, but also want to be tentative in order not to force their conclusions too strongly on their readers. The reading in D6 covers this aspect of modal verbs.
Comments
Activity B6.1:
They all refer to future time. The difference is that 1b) is more polite than 1a), and in 2b) your ’coming’ is considered less likely than it is in 2a). In other words, 1b) and 2b) are more tentative.
Activity B6.2:
1. permission
2. ability
3. possibility
4. ability in general, but in fact this functions as a request
5. possibility in general, but the idea is that something sometimes happens
6. ability in general; the use of can is common with the senses. Here it would be possible (but less idiomatic) to say I see . . .