Delahunty and Garvey
that is marked for tense, if the clause is finite. In She should have been work-
ing on her term paper, should is the first auxiliary and its {-d} indicates that it
is in the past tense. You can convince yourself of the accuracy of this rule by
removing the past tense marker from should and placing it on any of the other
auxiliaries and main verb, e.g., She shall had been working on her term paper.
You should find that all other orders are ungrammatical. We discuss tense in
our chapter on Basic Clause Patterns.
Second, in interrogative clauses, it is always the first auxiliary that is
moved to the left of the subject. If we turn She could have been seriously in-
jured! into a question, it is the could (as the first auxiliary) that moves: Could
she have been seriously injured? Again, you can test the accuracy of our rule
by moving other auxiliaries to the left of the subject, e.g., Have she could
been seriously injured?
Third, in negated sentences, the negative particle not is typically placed
after the first auxiliary, e.g., He has not been studying very hard lately. Try
placing it elsewhere in the sequence to see what happens.
Modal verbs
If a modal verb occurs in a clause, it will, as we noted, be the first of any
auxiliaries that clause contains. Besides occupying the same sentential posi-
tion, modals express related concepts. These concepts include notions such as
(a) necessity, either logical or social (obligation): You must read the book; (b)
possibility, logical or social (permission): He may leave the room; (c) ability:
He can do long division in his head; or (d) intention, either definite or condi-
tional: I will/would/shall/should write another 10 pages today. What these modal
concepts all have in common is that they indicate the basis for the speaker’s
judgment or belief about the truth of the sentence.
We can view the {-d/t} at the end of the second member of each pair of
modals as a variant of the past tense inflection {-ed}. This allows us to regard
each pair (excluding must) as comprising a present and a past tense form. To
see why this is so, consider the phenomenon called backshifting. Backshifting
involves the change from present tense to past tense forms when direct speech,
e.g., John is flying to Toronto tomorrow, is converted into indirect speech when
the verb of the main clause is in the past tense: John said that he was flying to
Toronto tomorrow. Sentences involving modals require a shift from the basic
form to the past tense, {-d/t}, form: John will fly out tomorrow becomes John
said that he would fly out tomorrow.