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.
1 Answer
When used to speak of ideas, this and that are used in a kind of metaphor for proximity, as when this (near me) is compared to that (over there). Ideological distance, like physical distance, is relative, so there is much blurriness in general usage over when to use which demonstrative pronoun. However, if the speaker remembers the analogy of proximity between their use for ideas and their use for things in physical space, the proper & clearer usage will prevail.
SAM: Keep your friends close. Keep your enemies closer.
DAVE: That might be a good idea, but whoever said it could not have had many enemies, so bear this in mind: blood is a big expense. Do business with your enemies so that they become, if not your friends, then your associates.
SAM: That might be a good idea. Or how about this: why not have your son woo & marry one one of their daughters?
&c.