I'm really not getting the 'my children are too young to reason with therefore I smack them' arguement. Someone will have to explain this to me. We learn to reason and use logic by being reasoned with, and deferring this by smacking will result in the child taking longer to learn these skills. Won't it?
A PP also said that clapping or a loud 'arggh' to stop child in their tracks, instead of a smack, would terrify the child more than the smack. Really? Is a momentary loud noise as terrifying as someone taking a hand to you? My boy is unterrifiable. Cars backfiring, explosions going off, you name it, he doesn't flinch. A loud 'OI', though, will momentarily stop him. Momentarily. Whatever he is being stopped from doing, if a repeated action, is something he does because he wants my attention. Therfore I'll give him my positive attention rather than punish him for wanting it. There is no way I would smack him, as he has no reasoning skills yet, and would not understand why on earth I'd do that. I intend to be a source of unconditional love in his world and teach him through supervision and reasoning, not be a source of confusion. We teach by example and that example in our home does not include hitting, not ever.
You cannot know your childs emotions, and can't say you are not hurting them. Even if the punishment does not 'hurt' on the outside, you can't possibly know how they feel about it (and by extension, you) on the inside if they are too young to reason with themselves and tell you. I consider a child who stops his/her behaviour because they were smacked is simply deferring to, and recognising, your greater power over them and is not learning about their behaviour, how to control themselves to stop that behaviour, and how to reason with themselves and the outside world. It is terribly confusing having people who you love and who love you hold a powerplay over you. If you say you stop and talk to the child first, you are still smacking later, which stunts the ability to reason and to learn to reason. IMhO.