Briefly, Watsonian perspective is interior to the story: in-universe, from the point of view of Dr. John Watson, the biographer and friend of Sherlock Holmes. Doylist perspective is exterior, from the point of view of Sir Arthur Conan Doyle, author and creator of both Watson and Holmes.
For a meta fan like me, both are great fun when applied to the rich story potential of Doctor Who.
In the much-loved and apparently also reviled 50th Anniversary Special, ‘Day of the Doctor,’ the Doctor crosses his own timeline and changes his own past, somehow without actually changing his past, as he knows it at least. Events occur through timelines which earlier/later have no impact on the story or the character. This apparently drives some fans – who haven’t been paying attention to the last 50 years – out of their minds. I’d like to look at these story choices from both a Watsonian and a Doylist point of view.
Doylist is easiest, in this case. For story reasons, to retire an aging throughline and refresh the show’s potential, it was advisable – if not essential – to bring back Gallifrey and the Time Lords. RTD made a wise choice in tossing the Doctor’s baggage back in 2005, rather than weigh down a new generation of viewers with all those years of history. It made sense, it worked, and it gave the character a depth and gravitas he hadn’t had in decades.
At the time, there was no sense of longevity. Davies didn’t know if he’d get one season, or three, or get pulled after six episodes. Now, we know. The show, being infinitely renewable, could last another 50 years. Moffat made a wise choice in bringing the Time Lords back, with all the potential for new adventures and new conflicts they present.
From a Watsonian perspective, pasts and futures change all the time on Doctor Who. Rose gets to meet her dad; Amy gets to marry her non-existent boyfriend; Donna changes the world with the turn of a wheel; Martha lives an entire year that never happened at all. There’s no reason to think the Doctor couldn’t shake up his own life a little. Perhaps he needs all those years – and all that regret – to come back around and make a better choice. Perhaps he needs that perspective in order to see what could be done differently. The War Doctor believes he doesn’t have a future; but once he’s seen that future, his own potential reveals itself.
In the anniversary special, as in all anniversary specials, the Doctor meets himself, crossing his own timeline. From a Doylist perspective, this is just plain fun: fans love seeing prior Doctors again, particularly longer-term fans whose favorite has been away a while. (OH that cameo!!) They don’t affect former Doctors’ stories because it’s impractical, if not impossible, to go back and change those already-aired tales. From a Watsonian POV, past Doctors are unaffected by events because they’re anomalies, and not part of those Doctors’ worlds. The Doctors appear, they have the effect they have on their successor’s timeline, and they return to their own timestreams as if nothing happened – because as far as they’re concerned, it didn’t. The War Doctor regenerates, waking up to a universe where the war is over and Gallifrey is gone. With no memory later than his acquisition of the Moment, of course he believes he is guilty of its destruction. Of course he believes there was no other way. He grieves; he broods; he meets Rose Tyler, and embarks upon the journey that will bring him full-circle to a place where he can change.
Not a bad story arc for a time traveler, and it frees up Twelve to have all sorts of new and different adventures – and whether you’re Watson or Doyle, that’s a good thing.