I said I'd post this yesterday, at Sci-Fi Night... but livejournal was down. So that gave me time to elaborate on my argument.
The Doctor remembers every Doctor Who story ever told. Every episode, target book, comic strip and every game of companions and TARDISes you played as a kid. The universe he lives in has no record of it, because paradoxes and divergent dimensions and the time war have reset things. But the Doctor remembers and sometimes when he is sad it's because you've stopped being 8 years old and he can't run around the school playground with you anymore.
The above was a summery of this blog post:
Teatime Brutality: Canon and Sheep Shit: Why We Fight I highly recommend reading this. It's not just about Doctor Who Canon, but Canon in General.
Another good Blog Post on this subject is:
PaulCornell.com: Canonicity In Doctor Who who argues that everything in Doctor Who is "shiftable", and was made even more "shiftable" by the Time War.
I'll try to explain... The Doctor travels in time, so he's always influencing not only the past / present / future of the Universe, but also his own personal past / present / future. For example, Torchwood didn't exist in Doctor Who history until the Tenth Doctor met Queen Victoria. That's why it was never seen before Season 2 of New Who.
Paul's argument is summed up by this lovely quote:
"That doesn’t mean we lose the lovely thought that Doctor Who is all one big story. It’s one big and very complex story, that rewrites and contradicts itself. That was always the case. Only now it does it with purpose, rather than by accident."
Here are some more random but amazing quotes about the "Canon" of Doctor Who...
First off, a quote from Doctor Who itself, from the episode we will be watchign next week (The Unquiet Dead)
"Time is in flux. It's changing every second. Your cozy little world could be rewritten like that *snaps*."
-The Doctor
"It is impossible for a show about a dimension-hopping time traveler to have a canon."
-Steven Moffat, one of the writers for Doctor Who.
"Sherlock Holmes solved the case before I could, as I recall."
"Sherlock Holmes is a fictional Character," Trix pointed out.
The Doctor grinned. "My dear, one of the things you'll learn is that it's all real. Every word of every novel is real, every frame of every movie, every panel of every comic strip."
"But that's just not possible. I mean some books contradict other ones and-"
The Doctor was ignoring her.
-From The Gallifrey Chronicles by Lance Parkin.
The image below is inspired by a short coversation between the Doctor and his Companion in "The Unicorn and The Wasp" an episode from Season Four of the New Series. In this episode they meet Agatha Christie, which prompts the Doctor's companion that if Noddy is real. The Doctor replies that he isn't.
.