***** NOT A TEACHER *****
Hello, Nekozuki:
I have good news and bad news for you!
First, the bad news: the correct use of “who” and “whom” is very difficult for most people.
Second, the good news: in your sentence, almost everyone would say “who.”
a. They would be absolutely correct.
b. They would not, however, know the reason!
Since you want to know the reason, maybe I can offer some helpful ideas:
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To parse a sentence, make sure it is in regular order.
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So we have “I wasn’t sure I wanted to be ____.” (Remember: this order is only for analysis. Don’t speak like this.)
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Now let’s concentrate on the “I wanted to be ___.”
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Now it gets difficult.
a. I am sure that you remember that the rules tell us that after a linking verb (such as “to be”) one needs to use the nominative case. That is, we should say, “My friend is a pilot. I would like to be he.” (99% of native speakers in 2014 ignore this rule and use “him.”)
b. Thus, in your sentence, we should definitely say “I wanted to be who.” (“Whom” is wrong because it is like “him.”)
- There are probably some speakers who say “I didn’t know whom I wanted to be” because they are trying to speak “good” English, but they do not remember the rule regarding linking verbs.
Well, I hope that my bad explanation helps you a little bit. If you are still confused, let us know. Maybe other members can do a better job in explaining it.
James
P.S. English is VERY difficult. Some native speakers joke that if they had not been born speaking it, they would never have been able to learn it!
For example, if you understood my words above, I have to tell you that the linking verb rule does NOT apply in a sentence such as “I do not want the waitress to be her.” (In this case, “she” is wrong. If you want to know why, please start a new thread, and someone will explain.)