When I was at school, we were taught that “this” and “that” were called demonstrative pronouns, and were used to distinguish objects from one another. I have grown up with this usage. However, nowadays there seems to be a different understanding of their meaning.

For instance, when one is at the checkout in a supermarket, it is fairly common to be asked “do you want a bag for that?” even if one has only purchased one item and it is lying on the counter between one and the shop assistant.

This puzzles me. In such circumstances it would seem more natural to me to use the neutral impersonal pronoun “it”, where it is quite clear what the person is referring to. Now, suppose instead I had bought several small items that would easily fit in my pocket, and one huge one – say some bars of chocolate and a large bottle of juice. It would then be OK for the assistant to say, pointing to the bottle, “do you want a bag for that?” although even then, since any putative bag would probably be used to accommodate all the purchases, the most natural word to use would be them.

Actually I don’t recall being sat down by a teacher or parent and taught all this – apart from the names of the parts of speech, which in any case occurred later. One learns by example; it is not usually all written down. Thus, for example, even if there were only one object that might be referred to, the circumstances affect the choice of words. If I were offering to help someone with a large suitcase at a station, I might say to them “do you want a hand with that?”– so what that tells me is that, if the object in question already has some sort of relationship with me and the other person, I should use it, but if not, that might be more appropriate, especially if the object is primarily related to the other person. If someone appears to have left something on the train (I spend a lot of time on trains, hence the plethora of railway examples) I might say “is this yours?” if I have picked it up, or otherwise “is that yours?” if the thing is some distance away.

On that basis, one would imagine that, if one receives a phone call and doesn’t recognise the voice, one should ask “who is that?” However, whenever this happens in an American film, the words used are invariably “who’s this?” which suggests that perhaps Americans use the words in a different sense. (Actually I’d love to be asked that question myself, as it would give me an opportunity to reply “Well, I’m sure that if you don’t know, I can’t tell you!”) The telephone is a classic case of a situation where one needs demonstrative pronouns – “This is Jim. Who’s that?” Presumably the American version of that remark would be “This is Jim. Who’s this?” which would sound a bit odd. Could it be that “Do you want a bag for that?” also has US origin?

As with so many other aspects of language, if the rules get bent and the distinctions between words are lost, then we tend to lose whole words (why ever use that if this will do?) and our language becomes blunter. Some people have already forgotten that there are other superlatives besides “great”.

What is saving these particular words at the moment is that clearly people can’t make up their minds which one to home in on. At the supermarket counter it’s that, on the telephone it’s this. Why not keep both, and preserve their discriminatory function too?

Then again, there is an alternative hypothesis. This is that the words are not being lost or over-used, they are just popping up in the wrong places, and the total number of them is conserved. The abundance of “thats” might simply be due to the fact that another usage of the word – as a subordinating conjunction, according to my dictionary – is on the decline. (An example of this usage of the word is the very occurrence of the word “that” in the preceding sentence: “the fact that …”) Pick up any newspaper and see how many times you would expect to see such a conjunction but it is not there. Probably most of these disappearances are down to editors trying to shorten word counts. But the result does not read well – not to me, at any rate.