Modals and auxiliary verbs in English

Old version (Fall 2006) - current version here


Modals

Historically, the modals of English, which are listed in (1), derive from a special class of verbs in Germanic (the ancestor of English and the other Germanic languages).

(1)     can, could, may, might, must, shall, should, will, would

Modals have always differed from ordinary verbs in Germanic, and in the course of the history of English, they have diverged from verbs even further, to the point where they now belong to a syntactic category of their own. Because many modals have meanings that are often expressed in other languages by verbal inflections, this syntactic category is called I(nflection).

In what follows, we review the ways that modals differ from verbs in English, both morphologically (what forms they exhibit) and syntactically (how they combine in sentences).

Range of forms

Modals and verbs differ in the range of forms that they exhibit. English verbs appear in a number of distinct forms (see Verb forms and finiteness), whereas modals have a single, invariant form. Modals never end in -s, even in sentences with third person singular subjects.

(2) a. * She { can-s, may-s } play the piano.
b. She { can, may } play the piano.

Modals also lack productive past tense forms. It is true that could, might, should, and would originated in Germanic as past tense forms of can, may, shall, and will. But today, only could can serve as the past tense of can, and that only in certain contexts.1


Example        Potential paraphrase

(3) a. Nowadays, you can get one for a dollar. = ... it is possible to get one ...
b. Back then, you could get one for a nickel. = ... it was possible to get one ...
(4) a. We can go there tomorrow. = It is possible for us to go there ...
b. We could go there tomorrow. =/= It was possible for us to go there ...
(5) a. You may ask the boss. = You are allowed to ask the boss.
b. You might ask the boss. =/= You were allowed to ask the boss.
(6) a. Shall I pick up some bread? = Is it a good idea for me to pick up some bread?
b. Should I pick up some bread? =/= Was it a good idea for me to pick up some bread?

Finally, modals lack present and past participles; the missing forms must be paraphrased.

(7) a. * { Cann-ing, may-ing } play the piano pleases her greatly.
b. { Being able, being allowed } to play the piano pleases her greatly.
(8) a. * She has { cann-ed, may-ed } play the piano.
b. She has { been able, been allowed } to play the piano.

Nonfinite contexts

A further difference between modals and verbs is that modals, unlike verbs, can't occur in nonfinite contexts (for instance, in to infinitive clauses or after another modals). Once again, the missing forms must be paraphrased.

(9) a. In to infinitive clause, modal * She wants to can speak Spanish.
b. paraphrase of modal She wants to be able to speak Spanish.
c. verb She wants to speak Spanish.
(10) a. After (another) modal, modal * She must can speak Spanish.
b. paraphrase of modal She must be able to speak Spanish.
c. verb She must speak Spanish.

Do support contexts

The inability of modals to appear in nonfinite contexts gives rise to three further differences between verbs and modals, all of them manifestations of an important phenomenon in the grammar of English called do support.

Emphasis. In the simplest case, do support affects affirmative sentences containing a finite verb whose truth is being emphasized. It involves replacing the finite verb by the verb's bare form and adding a form of auxiliary do to the sentence in the appropriate tense (either present or past tense). This form of do then receives emphatic stress, as indicated by underlining in (11).

(11) a. Unemphatic (without do support) He dances; she sang.
b. Emphatic (with do support) He does dance; she did sing.

By contrast, emphasizing the truth of a sentence that contains a modal is achieved by simply stressing the modal. Do support with modals is ungrammatical.

(12) a. Emphasis without do support He can dance; she will sing.
b. Emphasis with do support * He does can dance; she does will sing.

Negation. Do support with verbs occurs not only in emphatic contexts, but in two further syntactic contexts: negation and question formation. In both of these cases, the form of do that is added to the affirmative or declarative sentence doesn't necessarily receive emphatic stress (although it can).

In English, sentences containing modals are negated by simply adding not (or its contracted form n't) after the modal. Do support is ungrammatical.

(13) a. Negation without do support He { may, must, should, will, would } not dance.
b. Negation with do support * He does not { may, must, should, will, would } dance.

Sentences without modals, on the other hand, require do support in English. As in the case of emphasis, the verb appears in its bare form, and an appropriately tensed form of the auxiliary verb do is added to the sentence, followed by negation.

(14) a. Negation with do support He { does, did } not dance.
b. Negation without do support * He not { dances, danced }.
He { dances, danced } not.

Question formation. The final difference between modals and verbs concerns question formation. If a declarative sentence contains a modal, the corresponding question is formed by inverting the modal with the subject. Do support is ungrammatical.

(15) a. Question without do support { Can, may, must, should, will, would } he dance?
b. Question with do support * Does he { can, may, must, should, will, would } dance?

Again, however, in a sentence without a modal, question formation requires do support. That is, it is an appropriately tensed form of do, rather than the verb itself, that inverts with the subject.

(16) a. Question with do support { Does, Did } he dance?
b. Question without do support * { Dances, Danced } he?

Auxiliary do

This section summarizes the properties of auxiliary do, introduced in the previous section in connection with do support. Auxiliary do belongs to the same syntactic category as the modals---namely, I(nflection), because it shares their properties with one exception (in contrast to modals, it has an -s form).

The goal of the previous section was to establish the special status of modals, and we used the facts of do support as a criterion for distinguishing modals from verbs. In this section, we consider some of the same facts, but with a different focus. Rather than focusing on the distinctive properties of modals, we focus on the morphological and syntactic properties of auxiliary do itself.

Like all English auxiliaries (the others are be and have), auxiliary do is homonymous with an ordinary verb - in this case, main verb do. The examples that follow explicitly contrast main verb do with auxiliary do.

Range of forms

As just mentioned, the only difference between auxiliary do and the modals is that it has an -s form. In this respect, it patterns with ordinary verbs, including its main verb counterpart.

(17) a. Modal I can dance the polka.
b. He { can, * can-s } dance the polka.

(18) a. Auxiliary do I do dance the polka; I do not dance the polka; do you dance the polka?
b. He do-es dance the polka; he do-es not dance the polka; do-es he dance the polka?
(19) a. Main verb do I do the dishes.
b. He do-es the dishes.
(20) a. Other verb I dance the polka.
b. He dance-s the polka.

Nonfinite contexts

In all other respects, auxiliary do behaves like a modal rather than like an ordinary verb. For instance, it is ungrammatical as a to infinitive, after modals, or as a gerund. Notice the clear contrast between the judgments for auxiliary do in (22) and main verb do in (23).

(21) a. Modal, in to infinitive * They want to can dance the polka.
b. after (another) modal * They will can dance the polka.
c. gerund * Their canning dance the polka while blindfolded is unusual.
(22) a. Auxiliary do, in to infinitive * They claim to do dance the polka.
Intended meaning: They claim that they do dance the polka.
b. after modal * They will do dance the polka.
Intended meaning: It will be the case they do dance the polka.
c. gerund * Their doing dance the polka while blindfolded was unwise.
Intended meaning: That they did dance the polka while blindfolded was unwise.

(23) a. Main verb do, in to infinitive They want to do the dishes.
b. after modal They will do the dishes.
c. gerund Their doing the dishes was considerate.
(24) a. Other verb, in to infinitive They want to dance the polka.
b. after modal They will dance the polka.
c. gerund Their dancing the polka while blindfolded is unwise.

Do support contexts

Auxiliary do also behaves like a modal in do support contexts. Double instances of auxiliary do are ruled out, just like double modals are (see (10a)). Once again, auxiliary do and main verb do differ sharply, as shown in (26) and (27).

(25) a. Modal, after emphatic do * He does can dance the polka.
b. negative * He doesn't can dance the polka.
c. question * Does he can dance the polka?
(26) a. Auxiliary do, after emphatic do * He does do dance the polka.
Intended meaning: It is the case that he does dance the polka.
b. negative * He doesn't do dance the polka.
Intended meaning: It isn't the case that he does dance the polka.
c. question * Doesn't he do dance the polka?
Intended meaning: Isn't it the case that he does dance the polka?

(27) a. Main verb do, after emphatic do He does do the dishes.
b. negative He doesn't do the dishes.
c. question Does he do the dishes?
(28) a. Other verb, after emphatic do He does dance the polka.
b. negative He doesn't dance the polka.
c. question Does he dance the polka?

Auxiliary have

Let's now turn to auxiliary have, which combines with past participles (-en forms) to form the perfect forms of verbs. Auxiliary have behaves like a V with respect to its morphology and its occurrence in nonfinite contexts, but like an I with respect to do support. Specifically, auxiliary have, like auxiliary do, shares all the morphological properties of its main verb counterpart. In addition, it can appear in nonfinite contexts (unlike auxiliary do). With respect to do support, however, auxiliary have differs from its main verb counterpart and patterns together with the modals and auxiliary do. The complex behavior of auxiliary have can be captured by saying that it moves from V to I in the derivation of a sentence (see Chapter 6 for detailed discussion of V-to-I movement).

(29) and (30) show that auxiliary have, like auxiliary do (cf. (18)), behaves morphologically like its main verb counterpart in having an -s form.

(29) a. Auxiliary have I have adopted two cats.
b. She ha-s adopted two cats.
(30) a. Main verb have I have two cats.
b. She ha-s two cats.

Auxiliary have differs from auxiliary do (cf. (22)) and resembles main verb have in being able to appear in nonfinite contexts.

(31) a. Auxiliary have, to infinitive They claim to have adopted two cats.
b. after modal They must have adopted two cats.
c. gerund I do not regret having adopted two cats.
(32) a. Main verb have, to infinitive They claim to have two cats.
b. after modal They must have two cats.
c. gerund I do not regret having two cats.

On the other hand, just like auxiliary do (cf. (26)) and in contrast to main verb have, auxiliary have is ruled out in do support contexts.

(33) a. Auxiliary have, after emphatic do * He does have adopted two cats.
b. negative * He doesn't have adopted two cats.
c. question * Does he have adopted two cats?
(34) a. Main verb have, after emphatic do He does have two cats.
b. negative He doesn't have two cats.
c. question Does he have two cats?

Be (auxiliary and main verb)

The examples in (35)-(40) illustrate the behavior of auxiliary be, which is used to form the progressive (is coming, was dancing) and the passive (is abandoned, was sold) in English. Auxiliary be behaves just like auxiliary have. In particular, it has an -s form (irregular though that form is), and it can appear in nonfinite contexts, but it is excluded from do support contexts. As a result, auxiliary be can be treated just like auxiliary have: as belonging to the syntactic category V, but moving from V to I in the course of a derivation.

Main verb be differs from main verb have and main verb do in behaving exactly like auxiliary be. In other words, main verb be is the only main verb in modern English that moves from V to I.

(35) a. Auxiliary be, non-third person I am learning Spanish; I am invited to the ceremony.
b. third person She i-s learning Spanish; she i-s invited to the ceremony.
(36) a. Main verb be, non-third person I am happy.
b. third person She i-s happy.
(37) a. Auxiliary be, to infinitive They claim to be learning Spanish; they claim to be invited to the ceremony.
b. after modal They must be learning Spanish; they must be invited to the ceremony.
c. gerund2 I don't regret being invited to the ceremony.
(38) a. Main verb be, to infinitive They claim to be happy.
b. after modal They must be happy.
(39) a. Auxiliary be, after emphatic do * She does be learning Spanish; she does be invited to the ceremony.
b. negative * She doesn't be learning Spanish; she doesn't be invited to the ceremony.
c. question * Does she be learning Spanish? Does she be invited to the ceremony?
(40) a. Main verb be, after emphatic do * She does be happy.
b. negative * She doesn't be happy.
c. question * Does she be happy?

Summary

The table in (41) provides a synopsis of the morphological and syntactic properties of the items discussed here, arranged from most to least verb-like. As is evident from the table, the syntactic category of an item depends on whether it is the verb-like or the modal-like properties that predominate.


(41)     Ordinary verb< Be and
auxiliary have
Auxiliary
do
Modal

Has -s form yes yes yes no
Occurs in nonfinite contexts yes yes no no
Occurs with do support yes no no no

Syntactic category V V I I


Notes

1. More precisely, we must distinguish between form (morphology) and meaning (reference). Ordinarily, forms with past-tense morphology are used to refer to an event or state prior to the time of speaking. However, it is possible in English to use past-tense forms to refer to events or state contemporaneous with a reported time of speaking; this is the so-called sequence-of-tense phenomenon in reported speech, illustrated in (i).

(i) a. Direct speech:   She said, "They make too much noise."
b. Reported speech:   She said that they made too much noise.

As is evident from (ii) and (iii), can, may, shall, and will continue to maintain a productive morphological relationship with could, might, should, and would, respectively, in sequence-of-tense contexts.

(ii) a. Direct speech:   She said, "That may be so."
b. He told us, "You won't last long."
(iii) a. Reported speech:   She said that might be so.
b. He told us that we wouldn't last long.

Nevertheless, in keeping with the point made in the body of the text, the morphological relationship between the modals in (ii) and their counterparts in (iii) is purely formal, lacking the referential underpinning evident in (iv).

(iv) a.   They make too much noise.
b.   They made too much noise.

We thank Aaron Dinkin for drawing our attention to the sequence-of-tense phenomenon.

2. For reasons not well understood, gerunds of progressive forms, as in (i), are unacceptable.

(i)   * I like be-ing learn-ing Spanish.