Not that I ever really paid attention before, but for as long as I can remember, my standard Reference Desk greeting has been something like "Hi, can I help you?" Recently, one of my co-workers challenged me on this.
He said that me asking "can I help you" is not grammatically correct. Instead, I should be asking, "may I help you?"
I have never excelled at grammar, but I do enjoy semantic arguments. So, even though I didn't have a concrete reason for saying "can," I tried to see if I could spontaneously generate a legitimate justification that would appease even the grammar police. Here's what I came up with:
To me, when you ask a question starting with "may," it's is kind of like asking permission. "May I help you?" Yes, you may. But when people come to the Reference Desk (or call in), the action of them approaching me implies that permission to help them is granted - if they didn't want my help, they wouldn't ask for it.
So, with the permissions out of the way, the question truly does become "can I help you?" I might be able to, or I might not. It all depends on their question, their goal, and the resources available to us.
Which I felt justified my asking "can I help you?" But my coworker doesn't like to lose arguments, so while he accepted my theory, he pointed out that it would be more correct for me to ask, "how can I help you?" Since asking if I can help isn't what the patron wants to know, asking them how I can help gets to more to the point more quickly.
But since far too much thought has already gone into something as insignificant as this, I agreed with him and we both moved on; him still asking "may I help you?" and me still asking "can I help you?" Ah, intellectual progress.