It's the 50th anniversary of Doctor Who! Whovians everywhere are excited to see what the newest Doctor will bring to the character. That made us ponder the question: what makes the Doctor, "the Doctor?" Eleven different doctors have played the role over the past 50 years, and each was unique, with different personalities and characteristics. But besides the physical symbols surrounding him - the Tardis, the sonic screwdriver - are there larger cues that indicate the man is in fact "the doctor?"