Is it possible to replace 'which' with 'that' in the following sentence:

John's parents were unable to afford the surgery. They did the only thing they could think of, which was to make an appeal to the public.

Is it grammatical to use 'that'? If so, why?


No one has answered this completely here yet, so I will attempt to: the semantics are somewhat complex but can be understood in due time.

A restrictive clause is a phrase that contributes to the essential meaning of the sentence. For example, in the sentence "The painting in the hall that was blue was beautiful," "that was blue" is essential to the meaning of the sentence (there may be multiple paintings in the hall, wherefore it is necessary to include the distinguishing description) and therefore a restrictive clause. Contrarily, if there were only one painting in the hall, then this description would be unnecessary, and we would instead say, "The painting in the hall, which was blue, was beautiful," wrapping our non-restrictive clause inside a comma sandwich.

The words "which" and "that" are not always interchangeable. You may use "that" only with restrictive clauses and "which" with both restrictive and non-restrictive clauses (though it is generally more common to use "that" with restrictive clauses in American English). So the sentence "The painting in the hall which was blue was beautiful" is grammatical, whereas the sentence "The painting in the hall, that was blue, was beautiful" is not, for there is a comma sandwich setting off the clause "that was blue" and rendering it non-restrictive.

If you are not completely sure whether a certain clause is non-restrictive, just make it restrictive anyway, using, in accordance with your personal preference, either "that" or "which."

For example, consider a brown-furred dog running across the street. All of the following sentences regarding such a dog would then be grammatical, though emphasizing slightly different things:

  1. "The dog that was brown ran across the street." (emphasizes that the dog is brown)

  2. "The dog which was brown ran across the street." (still emphasizes that the dog is brown)

  3. "The dog, which was brown, ran across the street." (sets the color of the dog as a casual aside, unnecessary to the central meaning of the sentence)

  4. "The brown dog ran across the street." (the best, most concise version, for using "that" or "which" adds unnecessary verbose to the sentence)


Replacing "which" with "that" turns the second part into an independent clause, which in turn makes this a comma splice. If you were to also replace the comma with a period or a semicolon, then it would be grammatical, but it would be awkward.


No, "that" won't work in this case. I'd try to get rid of "which" altogether. "They did the only thing they could think of, making an appeal to the public." J.R.'s response also works.

It's not easy to explain. "Which" and "that" are relative pronouns which are (that are) sometimes interchangeable, especially with restrictive clauses. "He drives a car that he loves." or "He drives a car which he loves." My feeling is to get rid of them whenever possible: "He drives a car he loves." I can say "I hope that this is helpful," but it would be awkward to say "I hope which this is helpful." (I hope this is helpful.)

  • Could you explain why? We generally ask that answers include an explanation. This helps learners understand the rules and usage of the language. – Em. Jul 17 '19 at 2:59
  • Thanks for your explanation. I forgot to mention that you should edit your post to include the explanation (not the comments). Let me know once you’ve done that, or flag this conversation, so we can tidy up the comments. – Em. Jul 17 '19 at 21:34
  • I made the correction. Thanks for the help; I'm new here. – Brad Ryder Jul 19 '19 at 0:32

@J.R. answered in a comment:

If I switched the which to that, I would add an and after the comma:

  • They did the only thing they could think of, and that was to make an appeal to the public.

My own input:

Actually, (almost?) any separator would work (besides and), when changing which to that.

A colon:

  • They did the only thing they could think of: that was to make an appeal to the public.

A semicolon:

  • They did the only thing they could think of; that was to make an appeal to the public.

Maybe(?!) even a full stop (in this way, it looks to me more like a literary construct):

  • They did the only thing they could think of. That was to make an appeal to the public.

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