Quote Originally Posted by Gilbert
DBP: thanks, I knew it! It is perfectly clear that the "may I?/you may not" is not as common; as far as my question, I borrowed it from a Monty Python's sketch (where the answer was really snapped back (NO, YOU MAY NOT!).

Anyway, there seems to be a relation between can/have to and may/must, where the latter pair express an inner attitude, while the first one express pair is related to either a possibility or a necessity depending on an external factor, say a circumstance. That will explain why "can" and "have to" operate much more often than "may" and "must". Am I right?
This requires a great deal more thought for me, Gilbert and if you wouldn't mind, more explanation of what you're driving at. I think I follow you but ...