Modals, Prepositional and Particle Verbs,
Transitivity and Voice, and Conditionality
Before this discussion begins, it should be recalled again that the nine modal verbs can/could/may/might/must/shall/should/will/would are auxiliaries. Nonmodals be/do/have are also auxiliaries. One of the topics we will discuss in this section is the formal and the functional differences between modal and nonmodal auxiliaries as well as between both of them together and the category known as lexical verbs (LVs)—the vast majority of all the verbs in the language—that are not auxiliaries at all. Mention will also be made of peri[phrastic]-modals, that is, verb phrases that behave like modals but only in part. Consider the following facts:
a. Modals disallow do-insertion.
Because they are auxiliaries, modals do not allow do-insertion. The contrasts below exemplify this.
Do-Insertion: Presence And Absence
b. Modals do not inflect—they lack person, number, and tense.
The following conjugation proves that modals do not inflect whereas LVs do: