English Modal Verbs - Double Modals

Double Modals

In formal standard English usage, more than one modal verb is not used consecutively, as modals are followed by an infinitive, which they themselves lack. They can only be combined with non-modal constructions that have a modal function, such as have to, which in spite of its function is not a modal verb. Thus, might have to is acceptable, but might must is not, even though must and have to can normally be used interchangeably.

A greater variety of double modals appears in some regional dialects. In Southern American English, for example, phrases such as might could or ought to should are sometimes used in conversation. The double modal may sometimes be redundant, as in "I ought to should do something about it", where ought to and should are synonymous and either one could be removed from the sentence. In other double modals, the two modal verbs convey different meanings, such as "I might could do something about it tomorrow", where could indicates the ability to do something and might shows uncertaintly about that ability.

These kinds of double modal phrases are not regarded as standard, although a combination of a modal with a modal-like construction may be used instead. "I might could do something about it" is more often expressed as "I might be able to do something about it", which is considered more standard. Similarly used to could, which appears for example in country singer Bill Carlisle's 1951 song "Too Old to Cut the Mustard":

I used to could jump just like a deer,

But now I need a new landing gear.

I used to could jump a picket fence,

But now I'm lucky if I jump an inch.

is usually expressed as used to be able to. Double modals can also be avoided by replacing one of the modal verbs with an appropriate adverb, such as using probably could or might possibly in place of might could.

Double modals also occur in the closely related Germanic language Scots.