One reader has asked me to discuss the proper use of that,which, and who.
The issue of proper usage with these pronouns has three main elements, only the first of which will be addressed in the present article: (1) which of the three pronouns to choose for a particular type of antecedent; (2) which pronoun to choose for restrictive and nonrestrictive relative clauses; and (3) which case (who, whom) to choose for the pronoun who.
The second issue, the choice of pronouns with restrictive and nonrestrictive relative clauses, is part of the larger question of how to determine whether a relative clause is restrictive or nonrestrictive, in order to punctuate it correctly. I have written about that issue in a separate article, "Comma Usage: Restrictive vs. Nonrestrictive Relative Clauses."
The point we will examine in this article is the question of which pronouns can be used with which types of antecedents.
Here are the rules:
1. Who (and its inflections, whom and whose) is used to refer only to people or to entities treated as people (e.g., gods, or anthropomorphized pets).
One exception to this rule is that when it would be awkward to use the possessive phrase of which, the possessive whose may be used to refer to things, although a restructuring of the sentence will usually make even this exception unnecessary. Here is an example of whosecorrectly used to refer to a thing:
~That is the mansion whose three-hundred-year history has inspired so many local legends.
2. That is used to refer to animals, things, or people. Although as a general rule who is preferred for people, that is also acceptable for referring to people when the relative clause is restrictive, and sometimes using that will make the sentence read better.
~1. This is the boy who stole money from an old man who had gone out of his way to help him.
~2. This is the boy thatstole money from an old man thathad gone out of his way to help him.
~3. This is the boy thatstole money from an old man who had gone out of his way to help him.
~4. This is the boy who stole money from an old manthat had gone out of his way to help him.
Although all of four these sentences are "correct," the last two examples read better than the first two, because they avoid awkward repetitions.
3. Which is used to refer to things or animals, not people. When the relative clause is nonrestrictive, use who, notwhich to refer to people.