I want to be crystal clear and add much emphasis that something will happen if and only if a specific condition is met. I thought of If and only if and then and only then.
Can i use both in the same sentence to give emphasis to the condition that must be met?
Example:
"If and only if you are wearing your spacesuit, then and only then can may you exit the spacecraft."
Would a native speaker express in such a way to give emphasis or that would sound unfamiliar in English?
Best Answer
I'd say that it's OK. There's no grammatical rule that says you can't do this. I'm guessing that I've seen it done before - though I'd guess it's done more for comedic effect than in a serious way. I'm also pretty sure that I've seen someone say it in a comedic film, too.
I might make the suggestion to set off the "and only then" with an em dash or commas... this will make the stress of "and only then" even stronger.
If you really want to make it official, you'll want to use "may" not "can"... they certainly can leave the space craft without a space suit but it wouldn't be a smart idea.