§8.3 The preterite fonns of the modals 57In all three cases, the version without a modal is more assured than the one that has
will. The differences are related to the speaker's knowledge. The meanings con
tributed by will therefore belong in the epistemic family.5
8.3 The preterite fonns of the modals
Four of the modal auxiliaries, can, may, will and shall have preterite
fonns -could, might, would and should respectively. It is quite clear that they are
preterites, but it must also be stressed that they are highly exceptional in their behav
iour. We'll look briefly at both the similarities and the differences between the
preterites of the modals and other preterites.
(a) Similarities with ordinary preterites
Could and would can be used with past time meaning and in the subordinate part of
a remote conditional, and all four preterites are found in backshift:
[59] I asked him to help me, but he couldn 't/wouldn 'to
11 We 'd save a lot o/ money if you could/would cycle to work.
1lI I thought I could/would/%should/might see her yesterday,
but I had to work late at the offi ce.[past time]
[remote conditional][backshift]Note that backshift is obligatory in the context of [iii], so that it would be ungram
matical to replace the preterite fonns by present tense can/willfA'shall/may.^6
(b) Differences from other preterites
With other verbs the modal remoteness use of the preterite is restricted to a few sub
ordinate constructions, but with the modals it occurs freely in main clauses, in
examples like these:
[60] I could/wouldfA'should/might do it if they offe red to pay me.
ii Yo u could/might have been killed!
III Yo u should apologise.
iv Could/Would you help me move these boxes?
Example [i] is a remote conditional construction (the open counterpart being I
can/willfA'shall/may do it if they offe r to pay me). Both the modal auxiliary and
offe red are modal preterites, but while any modal preterite can occur in the sub
ordinate clause, only a modal auxiliary can occur in the main clause.5 With some predictions there isn't much doubt - e.g., when I say She'll be two tomorrow on the day
before a child's birthday. But there's no grammatical distinction between cases like this and cases like
the ones in [56]. In some varieties of English, especially BrE, shall is used with I st person subjects
as an alternant of will for future time situations, so we get %1 shall be glad when it's all over. This use
is epistemic. But the most common use of shall is in interrogative clauses like Shall 1 pick you up at
six? This shall is deontic because I'm asking you to tell me what to do.
6 Actually, some speakers do allow may here, which shows that for them the two forms have become
separated -might is no longer the preterite form of lTUly for these speakers, so it isn't substituted for
may in backshifting.