Is this the real life?
Is this just fantasy?
Caught in a landslide
No escape from reality
Flamboyant Queen frontman Freddie Mercury and father of modern philosophy Rene Descartes have two things in common: A predilection for exuberant moustaches and a nagging fear that it may ...like...y'know, all be just a dream.....
It's only Freddie, however, who seems to grasp the fact that this particular question isn't half as interesting as everyone thinks it is. ("Anyone can see.....Nothing really matters ......nothing really matters to me")
Even Descartes wants to consider the question of our dreaming / not dreaming existence only to the extent that he can get it all out of the way and get on with looking at optics or meteorites or static fluids or something, without some smart-Alec saying: "ah-ha... but what if it's all really...like....y'know..... a dream?"
In the end, Descartes decides life is not a dream, for the simple reason that God won't let it be a dream. (The Cartesian God is a bit like one of those English teachers at school who, with five minutes to go before the bell, regard it as rather bad form to write oneself out of a corner by suddenly ending a tale with the statement: "and then suddenly I woke up to discover it was all a just a dream"
It could be the case however, as Bishop Berkeley pointed out, that we are all living God's dream ....and in that case, it wouldn't matter half as much as you think it would : Wherever it is located, all Descartes and Berkeley need is a 'real' world that they can point to that is predictable and orderly and makes scientific sense, so that we can get on with the optics and the meteorites and the static fluids and stuff, in a way that appears coherent to everyone.........
Of course, this would mean nothing in the world of Doctor Who, which, asleep or awake, never makes any scientific sense at all. Back in the early 70's, when Jon Pertwee used to mutter about 'reversing the polarity on the neutron flow', there was at least an attempt to convey World-of-Who as a place which broadly complied with a range scientific principles - an understanding of which could help one repel this week's non-terrestrial invaders. Now, however, when folk can resist being converted into a Cyberman merely by thinking really hard about how much they really, really luv their kids or Davey Tennant can hurl a space lassoo around the world and pull it along with the Tardis, all pretense at a scientifically coherent outlook has gone.
No, if Doctor Who World is to have some consistent, coherent, predictable, shared reality, which its inhabitants can perhaps point to as an agreed 'non-dream' state, then it must conform to rules other than those of science. I would suggest that these rules are as follows:
1) All beings are in some way oriented to, or determined by, the Doctor. They all love him, or want to kill him (or, in the case of the Master, both)
2) Any being the Doctor encounters must in some way reflect some aspect of the Doctor's position, outlook or mental state.
So, within the confines of my my proposal, Father Christmas, as an, avuncular yet slightly-sinister seasonal visitor in outlandish clothing, who wants to give the Doctor a tangerine, CAN most definitely exist within a coherent World-of Who, but Danny Pink, as a fairly conventional young man who rather wishes that the Doctor would just quietly go away, is definitely a dream that Clara once had, probably whilst she was living inside a Dalek.....*
*I realise that the Danny Pink mournful soldier thing WAS written to reflect aspects of the Doctor, but I'd written myself into a corner, so don't stop me now, I'm havin' a good time, I'm havin' a ball....