Pain as Perception

The idea that pain is a perception rather than a sensation. See this Ted talk for a quick overview. It presents some examples that we could have damange without pain and pain without damage:

• A construction worker fell down a scaffold and had a large nail go over his feet. He was showing all signs of being in pain, however the nail had gone through the space between his 2 big toes, with no damage to the tissues.
• A solider in the American civil war had an arm blown off by a cannonball, and did show signs of pain. He only experienced and showed signs of being in pain 2 hours after the wound was repaired.