If people are nervous, they sometimes use “which” when “that” would do. Politicians often say “which” instead of “that,” to sound important. A writer may say “which” instead of “that”—it’s no big deal. It would be much worse to say “that” instead of “which.” Apparently the British use “which” more and do not see anything wrong with it. Americans have agreed to use “that” when the clause is restrictive and to use “which,” set off with commas, when the clause is nonrestrictive. It works pretty well.
An excellent example of a clause that everyone knows and that could be either restrictive or nonrestrictive is in the Lord’s Prayer: Our Father, who art in Heaven (Matthew 6:9). Is “who art in Heaven” restrictive or nonrestrictive? Just where is God? I think it is nonrestrictive, as indicated by the comma before “who”; that is, the phrase “who art in Heaven” doesn’t define the Father, it just tells where he lives. It is as if you could insert “by the way”: “Our Father, who, by the way, resides in Heaven”—except that “Our Father” is vocative, the grammatical term for direct address. In direct address there is no need to tell God where he is. In the original context, Jesus taught this prayer to his disciples. If there are no commas, the implication is that whoever is praying has another father (Joseph?). So conceivably Christ intended the phrase “who art in Heaven” as restrictive, to identify the heavenly father as opposed to the earthly one. Putting theology aside for a moment, I might say, speaking for my siblings and me, “our father, who art in Cleveland.” We would all understand that I was talking about our one and only dad, in Cleveland. New Testament Greek did without the commas, and the sense of it, in translation, has been up for grabs ever since. The Latin, which comes to us from Saint Jerome, is “Pater noster, qui es in caelis.” Nonrestrictive. You can hear the commas. The English translation, from the Book of Common Prayer (1662), makes it “Our Father, which art in Heaven.” Nonrestrictive, and thanks for the “which,” Anglicans, even if you did later change it to “who.” God here is the Creator, the Father in a figurative sense, and in a monotheistic tradition there is only one. But a modern Anglican version, dating from 1988, makes it simply “Our Father in heaven,” which is restrictive: our heavenly father, not our earthly one. One modern English version, both Catholic and Anglican, from 1928, does without the comma: “Our Father who art in heaven.” It’s a little weird, you have to admit: the restrictive one, without the commas, is more direct; it almost goes out of its way to snub the earthly father. The nonrestrictive, with the commas, is acknowledging that he is the father of us all and making note of his whereabouts.
I’m not religious. But isn’t this nearly mystical?
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After my first big catch at The New Yorker, I latched onto the coattails of my friend Nancy Holyoke, whom I’d met in the editorial library, where we’d both been initiated into the sisterhood of the rubber thumb. She had moved up to collating, and finally, after three years of indexing, I got a chance to join her in that department. In collating you transferred changes from the editor, the writer, the proofreaders (usually two), and the fact checker onto a clean proof for the printer. It was not a job I was born for: it demanded legible handwriting, and my penmanship had been deteriorating since third grade.