I'm not looking at any other replies because I know they will just make me want to argue and its too late for that. But I currently go to Karen Pryor Academy for dog training and behavior. We prefer the term Progressive trainers, because the one trainer was correct, you cannot be a purely positive trainer. We believe in positive reinforcement!!!! and NEGATIVE PUNISHMENT! Like if my dog were to pull on leash, I wouldn't correct, but I would stand and ignore until my dog stopped pulling, then continue on. (While reinforcing for llw) Negative punishment means we take something away to lessen the chance of the dog doing the unwanted behavior again. Ignoring the puppy when it bites. When it stops, resume play. There will always be punishment, I just choose not to correct my dog. This gives the dog the chance to try different things to get rewarded. My dog isn't afraid of being corrected for trying something. Extremely helpful when they are learning. My dogs quickly learn that they get rewarded for loose leash and get things taken away from them for tight leash. I honestly believe all dogs can be trained with positive reinforcement, negative punishment, however not all dogs can be trained with positive punishment.

Forgot to show you kikopup. she's an amazing trainer with an amazing youtube library. She came up with the term 'progressive' dog training.

http://www.youtube.com/user/kikopup?blend=1&ob=4