Turil: Over the course of the entire run of Doctor Who, what do you think has been the most valuable moral/message that the show has offered the world?
Neil Gaiman: You can think your way out of your difficulties.
This obviously isn’t exclusive to Doctor Who, but it’s definitely one of the primary memes that the show offers us.
The more evolved you are as a species, the more you can solve your problems by thinking about them (testing out different options in your head and picking the ones that seem to lead to the most useful results). Timelords may be more evolved than any other species in the universe, but there are other species, including humans, who can do it too, at least sometimes. :-)
I’d also include in Doctor Who’s most valuable memes the idea that curiosity leads to having an amazing life, that having too much power over others makes you dangerous, and that anyone can be a hero given a little support.