3. Ghosts
For supposedly no overarching themes this series, Doctor Who recently has been all about ghosts. Well, actually, right from the moment that the Doctor 'died' on the beach. It began with the Doctor, a ghost himself, being wiped from all databases in 'Asylum of the Daleks', by Oswin, another ghost living inside a Dalek. Then the Doctor dealt with the loss of his best friends, the Ponds, before starting to chase the ghosts of Clara. 'Hide' included these themes slightly more concretely than others, but when we reached 'The Name of the Doctor', the subtle themes of Series 7 seemed to converge at the Time Lord's past. Ghosts, ghosts, ghosts galore. And it makes sense, really, for the 50th year of the show to focus on the past, of what's behind us, of what we've lost and showing the Doctor trying to chase it and hold onto it. One of the more subtle pieces of symbolism in Doctor Who, but if it's intentional, it's really quite ingenious.