may(=permission) and general permission which has already been given

Question

Can is used to talk about permission that has already been given or refused, and about things that are allowed by rules or laws. May is not notmally used in this way.

(from Practical English Usage 4th ed. by Michael Swan)

Can "Do we have his general permission (which has already been given) to smoke in his garden?" be paraphrased to "May we smoke in his garden?"? (Here, "general permission" means the permission to do something at any time .)

From P.E.U, I know "Do we have his general permission (which has already been given) to smoke in his garden?" can be paraphrased to "Can we smoke in his garden?".

Can "Do we have your general permission (which has already been given) to smoke in your garden?" be paraphrased to "May we smoke in your garden?"? (Here, "general permission" means the permission to do something at any time .)

From P.E.U, I know "Do we have your general permission (which has already been given) to smoke in your garden?" can be paraphrased to "Can we smoke in your garden?".

Answer 1

Both 'can' and 'may' are used to ask for permission and to grant or deny it:

• Can I?
• May I?
• You can.
• You may.
• You cannot.
• You may not.

One way these words differ is in secondary meanings. "I can" is used to refer to your own ability (eg "I can play the piano") or permission granted to you (eg "I can borrow my dad's car". However, "I may" can be used to mean you might do something (eg "I may go to the gym tomorrow").

Answer 2

When I was in school, English teachers would often make a big deal that "may" refers to permission while "can" refers to ability. A game they loved to play was that a student would ask, "Can I go to the bathroom?", and the teacher would reply, "I don't know. Can you? Oh, you mean MAY I go to the bathroom ..."

But among actual English speakers, including the most literate and fluent, "can" can refer to either ability or permission. "May" only refers to permission.

So you might say, "Jack can run a mile in 3 minutes", meaning he has the ability to do this. "You may take two pieces of cake" means you have permission to take two pieces of cake. By the pedantic English teacher's definitions, "You can take two pieces of cake" means that you are physically capable of doing it -- you are strong enough to lift two pieces, perhaps. But in real life, this would be understood to mean that you have permission.

So to directly answer your question: There is no difference in which word we use whether it is general permission or specific permission. If someone says, "You may use the park to play basketball" or "You can use the park ...", either way, it is not clear if that means "I give you special permission this one time" or "anyone has permission to use the park to play basketball at any time". You would have to use additional words if you wanted to specify which you meant.