Now that was a silly question. But Jarvis answers it anyway. "So that I may be able to identify you." There's a few screens popping up on the nearest console, one with the Doctor's two hearts beating on an xray. "There is a 98% probability that you are not from Earth." There's also some background....something. Jarvis isn't sure what that is. He's trying to analyze it but it's not something he can scan easily.