Have you noted that there are some grammar points which students ask us about but which most student textbooks don’t cover?
Recently a learner asked me to explain the difference between it is and this is as a sentence opener. It wasn’t the first time I’ve been asked about this. (Look. I just used an it-cleft!) Despite having answered this question before, I still felt it diffult to answer concisely. I limited my explanation to a brief set of examples which called attention to only one possible diffference: It is can be used to make a general reference, as in It’s sunny outside. This is can be used to refer to a more specific situation, as in This is so much fun! Thanks for inviting me on a picnic. However, those examples only paint a small part of the big picture.
The following might be a better set of examples to discuss:
- Set 1: Use of it to refer back to an inanimate object or animal. She has a dog. It‘s a poodle.
- Set 2: Use of it in a subject position to make general statements. It’s cold. /It’s 9 o’clock. / It’s time for bed.
- Set 3: Use of this to refer to a specific situation or thing that’s close to the speaker either in time, space, or attitude. Shh! This is my favorite part of the movie! / Hey! This is what I’ve been looking for. / This is wonderful. You’re such a great cook!
- Set 4: For comparison: Is this a real Picasso painting? It‘s not authentic, is it? I’m no expert, so it‘s hard for me to tell the difference.
For students who need to understand structures through formulas and labels, we could share the basic definitions of a dummy subject and an it-cleft.
- A dummy subject is just a placeholder. It often stands in the subject position, but the actual subject comes after the verb. It can be a dummy subject, but this can’t. Example: It’s not easy to answer all questions concisely. [“It” is the dummy subject for “to answer all questions concisely.” = To answer all questions concisely is not easy.] Biber et al (2007) explore how it can have an anticipatory function. As a dummy subject, it can be paired with an adjective or adverb phrase, often to communicate the speaker’s view. More examples: It’s important to listen to your students. /It may be that I left out a few details.
- An it-cleft creates a sentence in two parts. The cleft is it + form of BE. The other part has the main content and a relative clause. Example: It was a reader who helped me discover the answer. In this statement, we can’t move the main content to the subject position as we could in statements with a dummy subject. Note that we have it-clefts. We don’t really have this-clefts – or do we?
I turn to you, my readers, to help me paint the full picture. Looking through the work of Biber et al, I see discussion of “demonstrative wh- clefts” (2007: p.961). Hm. Would this account for the kinds of sentences in which we can use either it or this (or even that)? Would you agree that the following are all correct?
- I decided to write about cleft constructions. It’s a grammar point which has been troubling me. / This is a grammar point which has been troubling me.
- Are you sure this is what you want? Yes, it’s what I want. / Are you sure it’s what you want? – Yes, I’m sure this is what I want.
I think when it and this have a stronger role as a reference word (i.e., it’s clear what is being referred to), then they can be interchangeable. But when it is being used merely to focus on the main content of the given sentence, this cannot substitute: It was a reader who helped me discover the answer. (Focus on a reader.)
Biber, D. et al. Longman Grammar of Spoken and Written English. Longman, 2007.
Biber, D. et al. Longman Student Grammar of Spoken and Written English. Longman, 2002.