Uncle Jazzbeau’s Gallimaufrey

that than which

You all know the drill. Use that in restrictive relative clauses and which in nonrestrictive ones. Example:

1. All the cars that were purchased before 1995 need to have their airbags replaced.
2. All the cars, which were purchased before 1995, need to have their airbags replaced.

In the first sentence, the information in the relative clause restricts which cars we’re typing about, but in the second sentence, we’re merely throwing in an extra factoid about a group of autos that has been defined in an earlier sentence (ungiven). [This example comes from Bryan A. Garner’s Dictionary of Modern American Usage, p. 648.] For a bit of hilarious hoof in mouth disease amongst the grammarian sticklers search for restrictive and unrestrictive (not a word) in Google. Whether restrictive and nonrestrictive relative clauses are better a matter of punctuation than grammar, I will not say. But here are some views from the experts:

Relation between that and which. What grammarians say should be has perhaps less influence on what shall be than even the more modest of them realize; usage evolves itself little disturbed by their likes and dislikes. And yet the temptation to show how better use might have been made of the material to hand is sometimes irresistible. The English relatives, particularly as used by English rather than American writers, offer such a temptation. The relations between that, who, and which have come to us from our forefathers as an odd jumble, and plainly show that the language has not been neatly constructed by a master builder who could crate each part to do the exact work required of it, neither overlapped or overlapping; far from that, its parts have had to grow as they could.

[...]

The two kinds of relative clause, to one of which that and to the other of which which is appropriate, are the defining and the non-defining; and if writers would agree to regard that as the defining relative pronoun, and which as the non-defining, there would be much gain in lucidity and in ease. Some there are who follow this principle now; but it would be idle to pretend that it is the practice either of most or of the best writers.

[H. W. Fowler, A Dictionary of Modern English Usage, second edition, pp.625f.]

As usual, Fowler has it both ways and brilliantly. Earlier in the last century, Professor Jespersen observed:

In early Modern English that is the favorite relative and is found in non-restrictive as well as in restrictive clauses, but there is in literature a growing tendency to extend the sphere of the wh-words, which more and more oust that from non-restrictive clauses. Who and which reminded scholars of the Latin pronouns and came to be looked upon as more refined or dignified than the more popular that.

[Otto Jespersen, A Modern English Grammar, volume 3, p 80.]

And, I close with a quotation from the marvelous “Humble Petition of Who and Which” by Addison in The Spectator, No. 78, 30 May, 1711; cited by Jespersen.

3. My Lords! with humble submission, That that I say is this: that that that that gentleman has advanced, is not that, that he should have proved to your Lordships.

Go forth and use that and which properly. The future of the English language depends on it.