Humans battle malevolent alien influence every day. So many things eat away at our brains ignorance, political posturing, media manipulation, corporate propaganda. Last Christmas is a metaphor for the world at large only this time the ultimate battle lies within our heads. It's our responsibility to wade through the manufactured lies and find the reality hidden beneath the empty words and images. People choose whether to feed their brains or allow them to be fed upon. Modern tools of misdirection are sophisticated and like the Doctor, people must always seek out clues that something is amiss and question what they are shown and told. The Doctors role throughout Series 8 is not to give out answers but to teach us to ask our own questions. Clara is the acolyte on the road to enlightenment. She stumbles along the way but the Doctor never gives up on her and she learns to return the favour in the long run.