Who/whom + who relative clause

Solution 1:

I don't know the answer. To me, it sounds ungrammatical. But other sentences that as far as I can tell have the same grammatical structure do sound grammatical, such as "Which person who you have known do you admire the most?"

Sentences like "Whom has Floyd Mayweather fought?" are usually analysed as showing movement of the interrogative word from the normal object position to the front of the sentence.¹

In other words, we can write the structure of the sentence as follows:

"Whom₁ has Floyd Mayweather fought t₁?"

The "original" position of the interrogative pronoun is marked by t₁.

In some cases, interrogative words can take other words with them that are part of the same phrase. This is called "pied-piping."¹ For example, pied-piping of prepositions is optional in English, so both of the following sentences are grammatical:

a. Whom₁ has Floyd Mayweather fought [_PP with t₁ ]?
b. [_PP With whom]₁ has Floyd Mayweather fought t₁ ?

But pied-piping is very limited.² Not all phrases with an interrogative word can be fronted as a whole.

I'm not sure if a pronoun followed by a relative clause starting with a "wh"-word constitute a "phrase" for the purpose of this kind of thing. Even in a declarative sentence, a pronoun and a "wh"-relative clause can be separated by intervening, unrelated phrases. Consider the following sentence: "Edgware had met many men and women in his career who had killed another human in rage, drunkenness or – rarely, cold blood" (The Forbidden Degree, by Charles Bunyan).

It's possible that in some cases a relative clause is part of the noun phrase, and in other cases it isn't. SIL International's Glossary of Linguistic Terms says

A relative clause is not necessarily a constituent of the noun phrase containing the head noun it modifies.

Example

The plumber arrived who we had called earlier. (Who we had called earlier has been extraposed from its normal position after plumber and is not a member of the noun phrase containing plumber.)

Unfortunately, I have not been able to find any description of the grammaticality of pied-piping a "wh"-relative clause like "who was in his prime." To me it doesn't seem grammatical, but it might be unacceptable for other reasons, such as length or information structure.

The sentence would certainly be grammatical without pied-piping, if the relative clause were at the end of the sentence: "Whom has Floyd Mayweather fought in his career who was in his prime?"

But there are some sentences with a similar structure but different noun phrases that sound grammatical to me with pied-piping. I found the following example in a chapter from Hornstein, Nunes and Grohmann's Understanding Minimalism³:

12 a. Which picture that Harry bought did he like t

It also discusses the following example:

(15) Which portrait did she buy that Mary likes.

In (15), the relative clause has not moved with the rest of the WH and we find that 'she' and 'Mary' cannot be interpreted as co-referential. Note that (14) and (15) are structurally quite similar at LF [logical form] and this would account for the inability of co-reference in (13c). We need a little more, however, we need to prevent "pied-piping" the relative clause at LF. We can enforce this in various ways: e.g. Assuming that LF moves as little as it can get away with, or it is preferable at LF to modify variables rather than operators (all things being equal).

In conclusion, I don't know enough grammatical theory to say if it's ungrammatical. There doesn't seem to be any obvious reason why it would be. But it does sound unacceptable to me, and apparently to some other people who've commented on or posted an answer to this question.

References:

1. "On the Grammatical Status of PP-Pied-Piping in English: Results from Sentence-Rating Experiments," by Seth Cable and Jesse A. Harris.
2. "Pied-Piping: Comparing Two Recent Approaches", by Seth Cable [PDF]
3. "Chapter 2: Some Architectural Issues in a Minimalist Setting", by Norbert Hornstein, Jairo Nunes and Kleanthes K. Grohmann, apparently taken from some edition of the book Understanding Minimalism

Solution 2:

My logic would go like this:

1) Reduce the sentence to a simpler form. The main question we're asking is about whom Mayweather fought.

"[Who/Whom] has Floyd Mayweather fought in his career?"

In this case, you could definitely use "whom". The easy "idiot-check", if you like, is to substitute "whom" for "him" and rearrange the exact words to see if it still makes sense. Without changing any words , we could rearrange this to "Floyd Mayweather has fought him in his career." This would make grammatical sense, even if it is slightly ambiguous.

2) After that, you've got "...who was in his prime..." to add back in. This is definitely "who", not "whom". This sticks out to me as a perfect case for brackets. This would make for easier reading, would give some cues to someone speaking that they should alter their tone for this sub-clause.

That leaves you with:

"Whom (who was in his prime) has Floyd Mayweather fought in his career?"

Is it grammatically correct, Yes, more or less.

Does it flow? Not exactly.

You could alter it a number of ways.

• You could substitute the "his" referring to other fighters for "their", to help differentiate between Floyd Mayweather and other fighters.

"Whom (who was in their prime) has Floyd Mayweather fought in his career?"

• Maybe see if there's another way of phrasing what you're trying to say. e.g. would it be sufficient/appropriate to say:

"Which top-level boxers did Floyd Mayweather fight during his career?"

"Which boxers did Floyd Mayweather fight during their prime?"