Grammaticality – Can You Not Do That?

grammaticality

I've been told that the expression "Can you not" (Can/Could + subject + not + verb) is used in casual conversation but it's not grammatically correct. Is this the case?

I'm aware that it wouldn't be appropriate in a formal / written context. I've also heard that it's only correct when an interjection is between the subject and the verb (i.e. "Can you please not do that?" or "Can you, like, not do that?").

Also, would the use of "Could" make the expression appropriate for a polite request?

Best Answer

It may be more polite to say/ask: Would you not do that? Or Will you not do that? Could and can seem impolite, because they suggest that the other person might be incapable of doing something.

...would is more polite, because it expresses the idea of probability, and of willingness, and of the desire that something be done, whereas “could” is more in the realm of ability (yes I can).

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