This is true or That is true?

Question

When someone says something that you agree with, should you say "that's true" or "this is true"? I have heard people say it both ways. My question is for both formal and informal usage.

Answer 1

Hi. You are right, "this" and "that" are often used interchangeably even by native speakers like me. It's done out of habit, hearing other people do it, pop culture influences and other reasons. But if we look closer, each word does have a specific usage. We use the word "this" when we are talking about something belonging to us, that is near to us, or in some other way is in a close relation to us. Look at this sentence...

"This is my pencil."

I use 'this" because the pencil's is mine and is in my possession. Now look at another sentence...

"That is your pencil."

Now I am speaking from the perspective that the pencil doesn't belong to me, it belongs to someone else so I use "that" instead of "this". If the person I was talking to questioned whether the pencil was their', they would say "Is this my pencil?". So they will use "this" when talking about the same pencil where I used "that" as they are establishing the pencil has a relationship to them.

Now when talking about using sentences like "This is true" or That is true" the habit of using this and that interchangeably might be used here, but again it could also be a matter of establishing who said the statement that was true. If the speaker you are with says something that is true, it would make more sense to say "This (what you said) is true." and use "That is true." when talking about something a third person (other than the speaker and listener) said that is true.