ed or understood, if the noun
clause and the principal clause have _different_ subjects, the same
auxiliary is used that would be used were the subordinate clause used
independently: [I fear we _shall_ be late. My friend is determined that
her son _shall_ not be left alone].

2. In all other subordinate clauses, _shall_, for all persons, denotes
simple futurity; _will_, an expression of willingness or determination:
[He thinks that he _shall_ be there. He promises that he _will_ be there].

3. In questions, _shall_ is always used in the first person; in the second
and third persons the same auxiliary is used which is expected in the
answer.

(NOTE.--_Should_ and _would_ follow the rules for _shall_ and _will_.)

+61. Tenses for the Completed Action.+

1. To represent an action as completed at the _present_ time, the past
participle is used with _have_ (_hast, has_). This forms the _present
perfect_ tense: [I _have finished_].

2. To represent an action as completed in _past_ time, the past participle
is combined with _had_ (_hadst_). This forms the _past perfect_, or
_pluperfect_, tense: [I _had finished_].

3. To represent action that will be completed _in future_ time, _shall
have_ or _will have_ is combined with the past participle. This forms the
_future perfect_ tense: [I _shall have finished_].

+62. Sequence of Tenses.+--It is, in general, true that the tense of a
subordinate clause changes when the tense of the main verb changes. This
is known as the Law of the Sequence (or _following_) of Tenses: [I know he
means well. I knew he meant well].

The verb in the main clause and the verb in the subordinate clause are not
necessarily in the same tense.

[I think he _is_ there. I thought he was there.
I think he _was_ there. I thought he had been there.
I think he _will be_ there. I thought he would be there.]

In general, the principle may be laid down that in a complex sentence the
tense for both principal and subordinate clauses is that which the sense
requires.

General truths and present facts should be expressed in the
present tense, whatever the tense of the principal verb: [He
believed that truth _is_ unchangeable. Who did you say _is_ president
of your society?].

The _perfect infinitive_ is used to denote action completed at
the time of the main verb: [I am sorry _to have wounded_ you].

+63. Mode.+--A statement may be regarded as the expression of a fact