The "Who" vs. "Whom" Conundrum
Theoretically the decision between who and whom should be an easy one: use who if you need the subject form and whom if you need the object form. To determine with consistent accuracy which form you need, though, you must first have a good understanding of grammar in general and of sentence structure in particular.
The good news is that even if you feel shaky on those things, you can do pretty well using a simple substitution test. The following three examples, all of which require a who–whom decision, illustrate how the substitution test works.
Who/whom did you call?
In this case, the correct form is whom. The grammatical explanation is that the pronoun is the direct object in this clause, so the object form is required. If you can’t immediately tell that by looking at the sentence, though, you have an alternative. Try the following instead:1. Reorder the words. Example A is a question, so the word order is inverted. Try rearranging the words so that the subject (the doer of the deed) comes first. Then proceed to the verb(s), and so on. You should end up with the following:
You did call [who/whom].
2. Now, instead of choosing between who and whom, try choosing between the personal pronouns he and him. (She versus her, or they versus them, would work fine as well.)
You did call [he/him].
The reason for this substitution is that most people’s ears are much more sensitive to the differences between the entirely familiar he and him than they are to who and the much less familiar whom.
3. Once you have chosen the correct personal pronoun — him in this case — you determine which form that is: subject or object. Since him is the object form, you need the object form in the original question: whom.
Whom did you call?
Some people are not comfortable using whom when they speak. If you have a hard time imagining yourself actually asking this question of a co-worker, that’s probably okay. In the twenty-first century, many people would say, “Who did you call?” — without suffering dire consequences. Whom is far less common in speech than it once was.
Nonetheless, whom has not been eliminated from the English language, and in writing it is still a good idea to preserve the who–whom distinction. Professional writers generally do.
Andrew, who/whom I admire, is an excellent actor.
Example B contains two clauses. Besides the main clause, Andrew is an excellent actor, there is an embedded relative clause, who/whom I admire.
In this case, the clause who/whom I admire is conveniently set off with commas. Take advantage of it! Mentally (or literally) cross out everything except the words between the commas, because the internal grammar of that clause is the only thing affecting the pronoun form.
1. Reorder the words so that the subject appears first.
I admire [who/whom].
2. Replace the who/whom above with he/him.
I admire [he/him].
3. Determine the correct choice between he and him, which is the object form him. That tells you that whom, which is also the object form, is the correct choice in the original sentence:
Andrew, whom I admire, is an excellent actor.
Andrew, who/whom I believe is an excellent actor, is waiting tables.
Once again, cross out everything except the words between the commas. Then:
ı. Reorder the words so that the subject appears first.
I believe [who/whom] is an excellent actor.
2. Replace the who/whom with he/him.
I believe [he/him] is an excellent actor.
3. Determine the correct choice between he and him, which is the subject form he. That tells you that the subject form who is the correct form in the original sentence:
Andrew, who I believe is an excellent actor, is waiting tables.