I searched the forums for this topic... found the "humiliation debate", which was interesting... so this question is similar...

What makes certain types of pain erotic vs. nonerotic?
I know most probably agree that a spanking is erotic, whereas stubbing your toe is not... But I was just wondering why... trying to figure out some definitive differences... no reason.. just for intellectual masturbation...

The question came to me when Master and i were joking that He might punch me (NO, He never would, it's a joke- that i started anyway), but it got me thinking... well, erotic pain.. a spanking or whatever, doesn't do any physical, permanent damage... well, neither would something like a punch, but that's generally nonerotic, I think most would agree... but being slapped in the face is erotic (not to all, I know), for example...

So I couldn't pinpoint why exactly... what's the concrete difference?

Any thoughts?