Can interrogative who be substituted by whom?

Question

Who are the letters for? (James Joyce, Ulysses)

It seems that who is moved forward to make an interrogative sentence, from after for. Then can you use whom instead of who, for the latter would be ‘whom’ when it comes after ‘for’?

Answer 1

Yes, it's an extracted object of the preposition for, with the preposition stranded. It's standard to use who, but whom is acceptable in this position. If you do use it, it makes the sentence more old-fashioned or formal-sounding. It can also be perceived as emphatic; this is because who is the usual choice, so whom draws attention to itself.

For more information about the historical distinction between who and whom, and to learn how it has changed over time, I suggest reading this Language Log post by Arnold Zwicky.