I’ve lighted on a use of the word “which” that has interested me.
“‘Doctor’ means a learned man, which I suppose this man is.”
Of course, when we talk or write about people, we use “who” or “whom,” so does this “which” refer not to the learned man himself, but to the condition of being learned? I’m certain I’ve used “which” in a such a way, but is it grammatical?
The sentence:
'Doctor' means 'a learned man', which I suppose this man is.
is perfectly grammatical, because the antecedent of "which" is "the condition of being a learned man", which -- being a condition -- is not a specific person. The indefinite article makes the noun phrase sound like a quality, as if it were adjectival (the quality of a person) rather than nominal (the name of a person).
Another example:
There is also a grammatical reason why "which" and not "who" or "whom" is correct, and that is the function of the antecedent in the relative clause -- subject complement:
I suppose this man is a learned man.
He is a liar.
Instead, if the function of the antecedent within the relative clause is "more nominal", so to speak (for example subject or object), then "who" will be used:
He is so aggressive people call him Hitler, who I think was much more cruel than he is. (Hitler was much more cruel.)
He is so talented people call him Da Vinci, who he studied a lot about. (He studied a lot about Da Vinci: object to the preposition "about")
In the two sentences above, while the proper name is used as a quality in the main clause, the proper name recovers its full meaning as the designation of a specific person in the relative clause, and this accounts for the use of "who".
Which is correct, since it refers to learned, not man. What is the man? The man is learned.
But:
While, like you, I prefer to use who and whom for people and that and which for things. It seems unkind and inaccurate to treat a person like an it.
Unfortunately, the rest of the world hasn't come around to our point of view. There's no consensus about which one is correct. You'll hear it and see it both ways.
As my sister always told her kids when they said "It's not fair!": life isn't fair.
It seems to me that which is used here because a learned man is not a specific person. Compare it with:
He thinks that he is Napoleon, who I suppose would disagree.
Here, which would be wrong.
This use of which is grammatical and is commonly employed in spoken or informal English.
This type of which-clause is different than the one we use to modify a preceding non-person noun; this one modifies an entire proposition.
Some examples should make this clearer. Here is a which-clause modifying a preceding non-person noun:
The goat was standing on the roof of the house, which was abandoned.
Here is a which-clause modifying a proposition:
The goat was standing on the roof of the house, which didn't make sense.1
We can look at it another way . . . Here is a who-clause modifying a preceding person noun.
The people were dissatisfied with their leader, who was soon fired.
Here is a which-clause modifying a proposition:
The people were dissatisfied with their leader, which was warranted.
Not:
*The people were dissatisfied with their leader, who was warranted. (incorrect)
The OED specifically calls out this usage:
which, pron. and adj.
III. Relative uses . . . 7. pron. c. Referring to a fact, circumstance, or statement. Now very common in spoken English.
Source: Oxford English Dictionary (login required)
1. Goat sentence examples from Grammar-Quizzes.com: Which Clauses—Modify the preceding noun versus the idea of the entire clause.
