He must decide who/whom to be. Which is correct?

Question

Which of the following two sentences is correct?

He must decide who to be.

He must decide whom to be.

I can think of arguments for both sides, but I'm not sure.

To elaborate, is who(m) the object of decide, the subject of be, or the object of be? Does the infinitive form of be have any bearing on the answer? And is there anything else to consider about the position or role of who(m) in this particular sentence that would inform the answer?

The answers to the linked question What’s the rule for using “who” and “whom” correctly? say to "substitute he and him for who and whom." However, that doesn't give a clear answer in this context, because neither of those pronouns sounds right: "He must decide to be he"? "He must decide to be him"? Normally we'd use a reflexive pronoun here ("He must decide to be himself") and it's not clear what case that corresponds to.

Answer 1

The Wikipedia link about the accusative case explains that

Modern English, which almost entirely lacks declension in its nouns, does not have an explicitly marked accusative case even in the pronouns. Such forms as whom, them, and her derive rather from the old Germanic dative forms, of which the -m and -r endings are characteristic.

Now, whether to use who or whom in your sentence entirely depends on which case should be used, accusative (whom) or nominative (who).

In English, it is grammatically correct to use nominative after the verb to be as in

It's he who stole my car. It's they who told me the truth. It's she who lied to me.

However, we know that "It's me" (using the accusative case after to be) is broadly used in English. But it is just a few exceptions.

In your sentence, it is appropriate to use the nominative case as it is the complement of to be. If you divide the sentence into two parts:

He must decide / He should be who => He must ask who he should be => He must decide who to be.

in the same way as:

He must decide / He should meet whom => He must decide whom he should meet => He must decide whom to meet.

He must ask / She is who => He must ask who she is. (This question cannot be shortened with wh-word + to-infinitive as the subjects are not same.)

We don't ask,

*Whom is he? or *Who is him?

*Whom am I? or *Who am me?

because whom and him/me are the accusative case and can't be a complement of the verb be in this case.

Note: "He must decide who he wants to be" is more idiomatic than "he must decide who to be".

Answer 2

It would be

He must decide who to be.

because

who

is a subjective pronoun and

to be

is a verb, and subjective pronouns have to be the subject of a verb. Whom is an objective pronoun, so it would have to be the object of decide, which it isn't. If it were to be the object of decide, the sentence would have to be written thus:

He must decide whom he will be.

This is an example, and

will be

could be exchanged for

is to be,
should be,

etc. as the writer desires.

Answer 3

When fronted "who" is a predicative complement, as it is in your example, it is always nominative.

Answer 4

He must decide who to be.

This is correct grammatically (but as noted elsewhere, it is not a sentence that you would see in general use, if ever).

He must decide who to appoint. // He must decide whom to appoint.

The latter is grammatically correct, however "whom" can run the risk of sounding archaic and/or pretentious, even when used in the proper way, so it is often reserved for really obvious instances where "who" looks or sounds distinctly incorrect.

Answer 5

He must decide who(m) to be.

We can tell that “who(m)” in this sentence isn't the subject of "to be" because the meaning of the sentence requires the subject to be "he" (or an empty element with "he" as the antecedent). It means the same thing as "He must decide who he will be" and not the same thing as "He must decide who will be."

I think this sentence has the same structure as a sentence like

He must decide [to be an adult].

In other words, the pronoun “who(m)” is the complement of the verb "to be". This corresponds perfectly with the meaning of the sentence. The position of the pronoun “who(m)” in front of “to be” is regular due to the process of fronting. If we mark the original position of the pronoun with a “trace” t₁, we get the following representation of the structure:

He must decide [who(m)₁ to be t₁].

Now, as mentioned in the question, both nominative and accusative pronouns sound odd after “decide to be” for semantic reasons.

However, if we compare this to other sentences containing "to be" with similar structure but different semantics, we find that the nominative seems to have been historically prescribed in this grammatical context. Correct English, Volumes 20-21, edited by Josephine Turck Baker, from 1919, says that the following sentences are "correct":

• It was supposed to be I who made the error.
• It was thought to be he to whom the speaker referred.
• I should like to be he/she.

I think this addresses Anonym’s point about “I want him to be here”: quite simply, Baker treats “to be” differently depending on whether it’s explicitly preceded by an accusative pronoun. And in a sentence like "He must decide to be an adult", there is no accusative pronoun, so Baker (and presumably other prescriptivists like her) would consider it incorrect to make the complement of "to be" accusative in this context.

As Rathony said in a comment, “The verb decide takes who to be as an object, not who itself.”

The fact that “decide” works this way is simply a fact about this particular verb in modern English.

Now, all of this rests on my original analysis of the structure of the sentence, which might be wrong (I'm not a syntax expert), although BillJ's answer seems to assume more or less the same structure I've presented here.

"Who" certainly sounds OK here, so even if I'm not 100% certain "whom" would be wrong, I'm confident enough to recommend "who" over "whom" here. As medica said in a comment,

Since whom is often misused as an overcorrection, the current recommendation is, When in doubt, use who. That way, if you make a mistake (either way), it will seem less pretentious.

Answer 6

In this context, "who he is" and "who to be" have the same meaning, just in different tenses. Assuming tense alone does not change the structure, they should both use who. Moreover, if be is here a linking verb, it may not be correct to assume it can be transitive. Only a transitive verb should need an object pronoun such as whom. For example, in "He must decide whom to marry", marry is a transitive verb taking whom as an object.

On the other hand, it appears that who/whom here is in the dative case, or the case of an indirect object. Generally speaking, indirect objects are always supposed to be in object form. One of the key features of indirect objects is that they can be omitted while keeping the sentence fully grammatical: "He must decide whom to be" -> "He must decide to be".