Modals and auxiliary verbs in English

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

However, they have differed from ordinary verbs throughout the entire history of Germanic. In the course of the history of English, they have diverged from verbs even further, and as a result, they are grouped in a syntactic category of their own. Because many modals have meanings that are also often expressed across 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 Verbs), whereas modals have a single, invariant form. For instance, 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 forms like could, might, should, and would originated in Germanic as the 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.

Example        Status of
potential paraphrase 		Potential paraphrase
(3) a. Nowadays, you can get one for a dollar. ok ... it is possible to get one ...
b. Back then, you could get one for a nickel. ok ... it was possible to get one ...
(4) a. We can go there tomorrow. ok 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. ok 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? ok 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 second difference between modals and verbs is that modals can't occur in nonfinite contexts (for instance, in to infinitive clauses or after another modals), whereas verbs can. 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 which concern an important phenomenon in the grammar of English called do support.

Emphasis. In the simplest case, do support occurs in affirmative sentences that contain a verb (without a modal) and whose truth is being emphasized. It involves using the verb's zero form and adding a form of auxiliary do with the appropriate tense (either present or past tense) to the sentence. 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 is obligatory not only in emphatic contexts, but in two further syntactic contexts as well: negation and question formation. In these cases, the form of do that is added to the affirmative or declarative sentence is not necessarily given emphatic stress (though it can be).

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. As in the case of emphasis, the verb appears in its zero form, and an appropriately tensed form of the auxiliary verb do is added to the sentence. In addition, negation follows the do form.

(14) a. Negation with do support He { does, did } not dance.
b. Negation without do support * 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 placing the modal before the subject, and 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 appropriate form of do, rather than the verb itself, that precedes the subject.

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

Auxiliary do

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

The goal of our earlier discussion 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, some of the same facts are considered, but with a different focus. Rather than focusing on the 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, so-called main verb do. The examples that follow explicitly contrast main verb do with auxiliary do. Notice that the do of do so substitution is the main verb.

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 main verb do.

(17) a. Modal I can dance the polka.
b. He can 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; I do so.
b. He do-es the dishes; he do-es so.
(20) a. Other verb I dance the polka.
b. He dance-s the polka.

Nonfinite contexts

In all other respects apart from the availabilty of an -s form, 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; they want to do so.
b. after modal They will do the dishes; they will do so.
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 (26) and main verb do (27) differ sharply.

(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; he does do so.
b. negative He doesn't do the dishes; he doesn't do so.
c. question Does he do the dishes; does he do so?
(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 us now turn to auxiliary have, which combines with past participles (-en forms) to form the so-called perfect forms of verbs. As we will see, auxiliary have shares all the morphological properties of its main verb counterpart. In addition, unlike auxiliary do, it can appear in nonfinite contexts. As a result, auxiliary have is categorized as a V, rather than as an I. However, with respect to do support, 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 4 for more detailed discussion).

(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 possible 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?

In summary, then, 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. It is this conjunction of properties that the verb raising analysis is intended to capture.

Auxiliary be

Finally, the examples in (35)-(40) illustrate the behavior of auxiliary be, which is used to form the progressive form and the passive in English. Since the present discussion is primarily concerned with auxiliaries, we begin by observing that 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 is treated just like auxiliary have: it belongs to the syntactic category V, and it undergoes verb raising.

Notice that main verb be differs from main verb have and main verb do in behaving with respect to do support just like auxiliary be. As a result, main verb be is the only main verb in modern English that has a verb raising analysis.

(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. gerund 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 lexical items discussed here, arranged from most to least verb-like.

(41)     Verb1 Be,2 auxiliary have Auxiliary do Modal
Syntactic category V V I I
Has -s form yes yes yes no
Occurs in nonfinite contexts yes yes no no
Occurs with do support yes no no no
1 'Verb' includes main verb have and main verb do, but not main verb be.
2 'Be' includes both main verb and auxiliary be.

Notes

in nonfinite contexts
For reasons not well understood, gerunds of progressive forms, as in (i), are unacceptable.
(i)   * I like be-ing learn-ing Spanish.