Grey's Anatomy, Season 5

Meredith:
[voiceover] In 6500 BC, some guy looked at his sick friend and said "I have an idea, why don't I drill a hole in your skull? It will make you feel better." And thus surgery was born. It takes a certain brand of crazy to come up with an idea like drilling into someone's skull, but surgeons have always been a confident bunch. We usually know what we're doing, and we don't, we still act like we do. We walk boldly into undiscovered country, plant a flag and start ordering people around. It's invigorating and terrifying.