What is it about surgery that called you to it as a vocation?
"Surgery is a specialty in which a person can be normal one moment then dying the next; I am there for the moment after that, returning to normal. That's fulfilling."
"We all have to start somewhere, and I started a while back. Along the way I've picked up a lot of experience beyond just the mechanical actions I was trained to do. Now I find that surgery still calls to me as a specialty in which the outcome may very well depend on who is there doing it, and I find it thrilling when a good outcome is because it was me who was there."
You can rest assured you're going to be asked a question similar to this. It's just an introductory exercise, so feel free to be pragmatic, philosophical, or both. As a therapy of last resort, surgery is a big deal. You should show the interviewer that you 'get it.'
"I find it fascinating, restoring function or preventing adverse events in a person; and, being that it's a person, the personal nature of it is part of my calling."