We have been on the topic of prepositions lately, and I have been asked to explain just what the preposition to is doing in a sentence like this: Who did what to whom? There’s quite a lot going on in that little five-word sentence, and a brief examination of it will remind us of some important points, both grammatical and rhetorical.
Prepositions, we remember, are those minute pieces of the language (linguists call them a kind of particle) that show the connection or relationship between things (the term thing in both grammar and philosophy refers to any entity whatsoever: a person, an object, or even an event). Our five-word question involves three things: someone acting (who), something done (what), and someone receiving what was done by someone else (whom). The first, someone acting, marks the subject of the sentence; the second, something done, marks the direct object of the verb did; and the third indicates what is called the indirect object, the thing not doing or done, but being done to. It’s this indirect object that concerns us most here.
Let’s reflect for a moment on just what it means grammatically to do something. If I do something to someone, if I congratulate or if I thank a friend of mine, the action of thanking or congratulating is thought to be going out from me, so to speak, and landing directly on my friend; the noun friend then would be termed the direct object of the verb to mark this target of the deed—I congratulate my friend, I thank my friend. Verbs of action that work this way are called transitive, and recognizing them is a very big deal in revising our writing, because it’s our job to be as straightforward as we can about who did what to whom.
Now where there’s action, there’s a scene, and a scene can involve someone other than, or in addition to, the direct object, the direct target, of the action. So in our original question, Who did what to whom?, the pronoun what is the direct object of the transitive verb did, and the pronoun whom is the object of the preposition to. A preposition and its object together form a prepositional phrase, and when a prepositional phrase begins with to or for, its object stands as the indirect object of the verb. The transitive verb did, then, has both a direct object (what) and an indirect object (whom). We can see the same thing more easily in this declarative sentence: I sent a letter to the company. The direct object of the transitive verb sent is letter, and the indirect object is marked by the noun company, the object of the preposition to.
But just here is where all this theory gets practical. If prepositional phrases with to or for can indicate an indirect object, that indirect object can also be written without the preposition—if (and only if) it is placed before the direct object. So instead of I sent a letter to the company, we could write I sent the company a letter, thereby avoiding a prepositional phrase and tightening the statement. The rule, then, is if a verb has both a direct and indirect object, the indirect object must precede the direct if the indirect is being conveyed without a prepositional phrase. (Some grammars, particularly the more traditional ones, call the indirect object a dative, employing the term used in Latin grammar to indicate a remote object, that for the benefit of which something is happening.)
And one more rule, which will take us to the question of the style, or rhetoric, of our original example. Why to whom and not to who? Because the object of a preposition must be formally in the objective case, and whom is the objective form of the pronoun who. To hew to that rule is to compose a higher diction, which is appropriate in certain circumstances and inappropriate in others. So could we ask, Who did what to who? Sometimes yes, and sometimes no. And that ambiguity shouldn’t annoy us as much as remind us that language always involves others, and that our relationship with others changes like everything else. Are there rights and wrongs? Of course. Are there rights and wrongs always? Of course not. And just where that line lies is up to you to decide.