Parenthetical Clauses 305
us consider what will be changed if the
if-clause is dropped. What will be actually lost is the information that he was not quite certain whether it was Hope after all. If it was not she, he could not assert that she had not heard him. So this
if-clause curiously vacillates between a conditional
and a parenthetical clause, and of course no choice between the two is here possible on grammatical, or, indeed, on any other grounds.
There appears to be no reason to deny that a parenthetical clause of this kind is a subordinate clause. If this view is endorsed there is every reason to suppose that a sentence consisting of a main and a parenthetical clause is a usual kind of complex sentence.
Parenthetical clauses introduced without any conjunction do not belong here and they will be considered in the chapter on asyndetic composite sentences.