The Doctor fled from a position of responsibility, stole a spaceship (or, in this case, storytelling medium), and ran off to have adventures. Except that instead of being a Time Lord from Gallifrey, he is the designated Master of the Land of Fiction - the writer and creator of all stories. And he’s gone on the run to live the stories instead of simply writing them.
Notably, this never quite gets contradicted, even when, later in this season, this shadow theme of The Mind Robber gets done as the main plot of two episodes. Because the Land of Fiction is outside of the universe, and because the Doctor fled it into the universe, he presumably became “real” instead of just fictional. And thus he became something else that served much of the same narrative function - instead of a wanderer in the dimension of narrative, he is a wanderer in the dimension of time. The Time Lords, with their “look but don’t touch” ethos and distance from the world, are a fair enough metaphor for the Land of Fiction itself. So the fact that, outside of the Land of Fiction, he is something else is hardly an issue.
In fact, it’s to be expected. After all, we navigate time, internally, through memory and stories, through our minds, which are, of course, far bigger on the inside than the mere lump of grey matter they appear to be externally. What is a Lord of Time if not the master of all things that have happened, and thus of all metaphors and stories? Except, of course, the Doctor storms out. Why? Because the Time Lords are far too narrow-minded. They are masters only of the stories that have happened. They cannot interfere and create new stories. And the Doctor is a Lord of all stories, real or imagined.
But more important than the fact that this theory can survive almost any canon challenge thrown at it is the fact that it makes sense beyond mere continuity. What defines Doctor Who is the fact that its story never has to end. That any story worth telling can be told as a Doctor Who story, and that there is no upper bound to the number of Doctor Who stories that can be told. Of course the Doctor is the destined and designated Master of the Land of Fiction. Who else possibly could be? What other person in the universe, real or imaginary, could possibly have the job of telling every story that ever was?
And that’s the genius of The Mind Robber. It comes at one of the series’ darkest moments - when its formula seems tired, its very ethics seem to be flagging, and when the entire cultural and ideological foundation for it appears to be crumbling the world over. And right in that moment, we get explicit confirmation of something that previously we had only hoped for and suspected. That Doctor Who is an idea that cannot be brought to an end. That there is always another story. Not just because of the flexibility of the premise or because the series has gone on long enough that it’s a cultural institution that is always going to be revisited as long as we have well enough recorded history to remember that it ever existed. No. Because the Doctor is every single story there ever was and ever could be, escaped out into the universe, and running loose bringing them into being.
This is, quite frankly, as powerful an idea as has ever been thought of in fiction. An idea that is far larger than fits in any one person’s imagination, even if that imagination is bigger on the inside. Something that, quite apart from anyone’s efforts to define it and create it, has taken on a life of its own. A symbol that has real power. A thought that has begun thinking for itself. A dream that no longer needs anyone but itself to dream it.
What if, in 1963, these things did occur? What if we held them to be true?
There are, after all, truths beyond mere canon