There are powerful arguments against using “whom” in modern writing. It’s archaic and it tends to stick out like the proverbial sore thumb in most places. But there’s a theory that you have to know how to do things right before you can decide not to. It worked for people like Joyce and Picasso, so it should work for us too.
Whom is the genitive or the ablative or something. I don’t actually know – that’s the sort of thing you learn if you study Latin, and all I can remember is “Caecilius est in horto,” which won’t get us very far. Anyway, we don’t need the proper word for it, just the proper usage.
The Trick (Questions)
Most of the times you could use whom are questions. “To whom did you give the last piece of cake?” for example, or “She was shot by whom?”
The trick to distinguish “who” questions from “whom” questions is to imagine a full answer using he / him*. If the answer uses “he” then the question should have “who”; “him” means you should use “whom”. In the above examples:
“To WHOM did you give the last piece of cake?” = “I gave the last piece of cake to HIM”
“She was shot by WHOM?” = “He was shot by HIM”
By contrast, “WHO shot her?” = “HE shot her.”
Be careful, though. When answering questions, especially when giving a one word answer, we often switch the sentence around. For example, if you were at a police line-up having witnessed a murder and the Detective said “Who shot her?”, you might well point to the perpetrator and say “It was him!” or simply “Him!”. So when using this trick, make the answer a full sentence using the same word order as the question.
Outside questions, you should just be able to do a direct replacement (he for who; him for whom). It will make for a slightly clumsy sentence, but of course you are not going to leave it with he / him, you are just temporarily using the substitution to check your word choice. A bit like we did with Advice and Practice .
“It was Jeremy who shot her” = “It was Jeremy, he shot her”.
“And God, by whom all things were made” = “And God, by him all things were made”.
*Footnote: Those who are bothered by gender issues will note I’ve gone masculine here. Yes, that means you will sometimes be using he/him for a female or non-gendered individual. If you prefer, she/her works for this trick, but I like he/him because the letter m reminds us that him is the substitute for whom.