After “To be”
“I knew it was him” is incorrect, because the word which forms the pronoun attribute of the verb was must be in the nominative case. But the infinitive of the neuter verb requires the objective case. Therefore we must say, “I knew it to be him,” not “I knew it to be he.” The latter faulty form is very frequently employed.
“Who did you suppose it to be?” Incorrect. Say, “whom.”
“Whom did you suppose it was?” Incorrect. Say, “who.”
The imperative mood requires the objective case after it. “Let you and I try it.” It should be, “Let you and me try it.”
“Let he who made thee answer that.”—Byron. He should have said, “Let him who made thee answer that.”
“Let him be whom, he may.” Him is the objective after the imperative let, and is correct. Whom should be who, as pronoun attribute of the verb may be. “Who he may be, I cannot tell,” is correct. “Who he may be, let him be,” is also correct. By transposing, and by omitting be, we have “Let him be who he may.”
“Let the sea roar, and the fullness thereof; the world, and they that dwell therein.” When, as in this case, the verb is widely separated from its object, we need to give particular care to the case of the pronoun which constitutes the object. They should be them.
Silent Predicate