The original sentence:

In fact, however, it is the untruthful thought which is the more vicious of the two.

The above sentence semantically appears to be:

In fact, however, the untruthful thought is the more vicious of the two.

If so, is there any particular reason to use "it is...which..." instead of the more common "it is...that..." structure in this context?

  • Your second sentence not only doesn't use that, but you've changed the word order—which makes a simple comparison between which and that more complex than it has to be. May 24, 2019 at 13:20

1 Answer 1


That is used for defining clauses (needed to provide meaning to the sentence), which is used for non-defining clauses (additional meaning to the sentence).


Which fork did you use? I used the one that was in the drawer.

Did you use a spoon or fork? I used the fork, which was a poor choice.

  • Karen, do you think it is an emphatic pattern, something like: It + be + underlined word/phrase + that/who/which clause?
    – Charlie
    May 24, 2019 at 1:56
  • @Charlie if I understand your question correctly, emphasis is shown by using an adverb (or adverb phrase) after that/who/which. "Did you use a spoon or fork? I used a fork, which, by the way, was a poor choice." "I used the one that, surprisingly, was in the drawer." To speak it, the sentence stress is on that/who/which with a brief pause before and after the adverb. P.S. "It + be" follows the same rules
    – Karen927
    May 24, 2019 at 2:40
  • @Karen927 In the UK, which can also be used in restrictive clauses. (Although even in the UK, that is not used in nonrestrictive clauses.) May 24, 2019 at 13:21

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