"Who he is," or "who is he" in noun clauses

I think who in the sentence you ask is not an interrogative pronoun.

Merriam-Webster's Dictionary suggests that, as a pronoun, who can mean " any person or persons that: whoever". This meaning is considered somewhat archaic by some dictionaries, though.

If you replace who in your original sentence with the definition above, you'll get:

In those days, we could not tell the person who was a friend and the person who was an enemy.

or

In those days, we could not tell whoever was a friend and whoever was an enemy.

The sentences above seem a bit awkward to me maybe because my idea is wrong. I'm sure that both Grammar Exchange ladies can give you a much better explanation.

Apple is justifiably puzzled by this apparent incongruity in the grammar rules. Because no grammar books that I know of treat this issue, it remains a mystery to teachers and students alike. The explanation is a bit complex, but I'll try to make it as clear as possible.

The direct question

(1) Who is he?

...has two noun phrases (here, pronouns): one that is known ("he") and one that is unknown ("who"). When the question is converted to a subordinate clause, the word order of the verb and the grammatical subject is statement order:

(2) We cannot tell who he is

The grammatical subject is "he." "Who" is the subject complement. So far, so good. The unknown item is "who" and the known item is "he". 'He" is the person we are referring to.

Now let's look at

(4) In those days, we could not tell who was a friend and who was an enemy.

Here we have the verb before the second noun phrase, in the same order as the direct question. What's different?

In (4) we don't have any "known" item. There is no noun phrase (like "he") to refer to. The "who" is unknown, and the noun phrases "a friend" and "an enemy" are also unknown. "Who" is the grammatical subject of the subordinate clause, not the subject complement as in (2).

"Who"in (4) means "which person among the group of potential friends or enemies." The sentence means

In those days we could not tell which person [among the set of potential friends or enemies] was a friend and which person [among the group of potential friends or enemies] was an enemy

The information "was a friend" and "was an enemy" is "new" information. It is the predication--what is said, or predicated, about the grammatical subject.

All right, I told you it was complex (it took me a long time to work it out some years ago). Is it clear now? If not, I'll make another attempt.

This kind of question is subtle but important, and it's good to have an answer for inquisitive students.

Marilyn Martin

Thank you for your replies, Marilyn and PromegaX.

Things are much clearer now．The following part seems to be the key to understanding this puzzling structure.
***********
In (4) we don't have any "known" item. There is no noun phrase (like "he") to refer to. The "who" is unknown, and the noun phrases "a friend" and "an enemy" are also unknown. "Who" is the grammatical subject of the subordinate clause, not the subject complement as in (2).

"Who"in (4) means "which person among the group of potential friends or enemies." The sentence means
*****************
Before posting this inquiry, I wondered if "a enemy" and "the enemy" would make a difference. Are both (A)and(B)correct? These sentences are the same patterns except for the determiner "the". They both seem to work, but if so, in what situation should we say which?

(A) We couldn't tell who the enemy was.
(B) We couldn't tell who was the enemy.

apple

Here's the difference:

(A) We couldn't tell who the enemy was. = We knew we had an enemy, but we couldn't tell his/her/their identity

In (A) the noun phrase "the enemy" is given, not new, information.

(B) We couldn't tell who was the enemy. = We knew that there were people out there, one or more of whom could be our enemy, but we couldn't tell which of them (who among them) was the enemy

In (B) the noun phrase, "the enemy," which is the complement of "who," is new information.

Marilyn Martin

So,
(A) He doesn't know who his mother is.
means he doesn't know the identity of his mother for a reason such as having been adopted when young.

(B) He doesn't know who is his mother.
means there are several women who seem to his mother, but he is not sure which woman is his mom. "Who" is an unknown pronoun and so is "his mother" in this case. But I have an impression (B) somehow overlaps with (A) in that "he" doesn't know the identity of his mother.

(B) can be rephrased as "He doesn't know which(woman) is his mother.", but (A) can not be rephrased as *"He doesn't know *which his mother is."

Getting back to my original sentences, (1) and (2), we can say both sentences are grammatically acceptable, but the meanings are different as explained in the previous posts by Marilyn Martin. Is this correct?

(1) In those days, we could not tell who was a friend and who was an enemy.
(2) We could not tell who a friend was and who an enemy was.

apple

Apple's understanding is correct. In both (A) and (B) the identity of the mother is not known, but in the second case, there is a set of candidates implied.

Marilyn Martin