"For the simple fact that I am not human." Before the man could doubt, the Master grabbed the stranger by his hand by the wrist and pulling open his business jacket he placed the man's hand on his chest to the far right.
"Heart number 1." The Master said. Then pulling the man's hand to the far left, he let him feel his other heart beating. "And heart number 2."
The Master then released the man's wrist letting him pull back. "I am a Time Lord. My race was conquering time while yours was still twitching in the primal ooze wondering, gee, is today a good day to develop limbs to crawl out of our muck?"
The Master his brief rant exhausted sighed. "And I am the last of my kind." The Master gave a half shrug. "Well, me and the killer of our species, the Doctor." The Master was surprised to hear a note of bitterness in his own voice. Maybe he wasn't as blase as he first thought about the Doctor destroying all of Gallifrey?