A Japanese student of mine emailed me with an English question yesterday, asking:

“There’s no sense ( in, of ) carrying on that way.”
The answer is “in”. But, I couldn’t make sense this meaning clearly. Is it some kind of construction of a sentence?
“in …….way” means like “in that way”??? But, if so, how about “carry on”(=go on)???

It was interesting for me to think about how we use “in” and “on” in English beyond “I live in Japan” or “I’ll go there on the 5th”. Here is my reply:

“There’s no sense in (doing something).”

It means “in this situation” or “in these circumstances”. You’ll often see in buildings “In case of fire, do not use lifts” which is very abbreviated English. I suppose that “in” means “while this is the case/is happening” or something like that. Also “Just in case…” and probably many other examples.

“Carry on” means “keep going” or “(yes you may) go ahead”. Also there’s “keep on going” which means “don’t stop”. Whereas “in” encompasses not just a physical “inside” but gives us the imagination of being in a situation, “on” puts us “on stage” where something is currently the focus of our attention. For example, we “put on a record” or “put on a cd”. The latter came from the former, as you physically had to put the record on the player. We also have “It’s on TV”.

So in summary (ha!): “In” encompasses a situation. “On” refers to an event currently happening that is our focus.