English grammar - Roger Berry 2012

B6.2 Modal auxiliaries
B6 Modal auxiliaries
Section B Development

There are nine ’central’ modals: can, could, may, might, will, would, shall, should, must.

They are easy to identify as they all possess the following formal features:

□ they have only one form; unlike verbs (and the primary auxiliaries) there is no infinitive, past tense, third-person -s form, -ed or -ing participle.

□ they are followed by the bare infinitive of verbs: I can see.

□ they form negatives directly with not: I may not come (See A7.)

□ they invert to form questions: Can I come? (See A7.)

In these last two respects they are like the primary auxiliaries. But unlike the primary auxiliaries they do not combine with one another; only one modal is possible, as the first element in the verb phrase.

There are a number of other forms which share some of the features of modals, and other verb-like expressions which cover the same meanings as modals. These are discussed below under the headings ’marginal modals’ and ’semi-modals’.

Modals and past time

Activity B 6.1

Look at the following pairs of sentences:

1. a) Can you come tomorrow?

b) Could you come tomorrow?

2. a) I may come.

b) I might come.

What time reference do they have? What is the difference between them?

In the past it was common to match up the modals in present tense/past tense pairs: can/could, may/might, will/would, shall/should. While there is a historical justification for this, such a position is no longer tenable (and what would the past of must be anyway?). The relationship between, for example, can and could is not the same as that between a present/past pair such as see and saw. All the so-called ’past tense’ modals, like could and might above, can be used for future time, which is not possible for the past tense of main verbs (apart from exceptional cases). For this reason we prefer to talk about the modals one by one.

However, there is something in common between the past tense and could, might, would and should. This is the idea of tentativity or distance that they can convey. For example, compare the politeness of might in

Might I have a look?

with that expressed by the past tense in

I wanted to ask you a question.

This distancing effect of modals is particularly true in reported speech: He can come/I said he could come). Here the difference is the same as the present/past distinction in main verbs. See B12 for more on reporting.

There are other past uses of could and would:

When I was young I could understand German. (a general past ability) After school we would go down to the shopping centre. (for past habits)

In addition, most modals can be combined with the perfect aspect to express past time: He must/will/would/could/may/might have finished by now.