Good ol’ who / whom. Here’s why whom is so difficult (and whom can be used as an interrogative / question word, as it is in this example, or as a relative pronoun, as in ‘The girl whom I saw laughed.’): the w-words (who, whom, whose, which; not so much what) are the only words in English that, no matter the grammatical function (subject, object, possessive), occur at the beginning of the clause, i.e. they are the only words in English that violate the most fundamental tenet of English grammar, that word order determines meaning or function. In the case of the w-words, word order does not determine meaning or function, but rather, like Latin, ancient Greek, and other inflected language, form / ending determines meaning / function.
When I introduce Paradise Lost and its language, I point the students to Book 1, line 238: him followed his next mate. And I ask a simple question: who followed whom? Most pause, as if to make certain that the answer is indeed as obvious as it seems, that he followed his next mate. But of course Milton, as not only one of English’s greatest poets but also merely an English speaker, would know one of the most basic rules of English, that he, rather than him, signifies the subject.
Rather, Milton, in a 400-ish year foreshadowing of Yoda, is going very Latin in his structure, letting the objective form him, rather than its placement in the sentence, determine meaning, i.e. it is not where him occurs that determines its function but rather that it is him (rather than he) that determines its function.
Whom functions the same way. Even as an objective form, it will occur as the first word of its clause, and that confuses us. Here’s a simple, albeit not entirely perfect, solution:
- If the w-word is followed by a verb, it is a subject and should be who.
- Who went home?
- Who saw the movie?
- The boy, who tripped, ran home.
- The woman, who won the race, smiled.
- If the w-word is followed by a noun / pronoun, it is an object (or at least a non-subject) and should be whom (or at least not who). You’ll note too that in the question-examples, the ‘whom’ is followed by a helping verb (did) but not the main verb (see and find).
- Whom did you see?
- Whom did the boy find?
- The boy, whom the ball hit, ran home.
- The woman, whom the runner beat, smiled.
- ‘What’ and ‘which’ are both simpler and trickier. As the neuter forms (‘what’ of the interrogative, ‘which’ of the relative), ‘what’ and ‘which’ function as both the subject and the object, but the rule still works.
- What happened? [subject, followed by verb]
- What did you do? [object, followed by noun / pronoun]
- The book, which was good, fell. [subject, followed by verb]
- The book, which I read, fell. [object, followed by noun / pronoun]