It has been a long-speculated and only recently confirmed theory that a Time Lord’s regeneration isn’t a completely random process. Ever since the Twelfth Doctor recognised his resemblance to a certain Roman merchant back from Series 4, fans have taken it upon themselves to figure out the Doctor’s subconscious reasoning behind his appearance and personality in each regeneration.
For the sake of being concise, I will only be covering the Doctor’s regenerations from the modern era of Doctor Who. While there is evidence for this theory in the classic series and in other Time Lord regenerations (such as the Master’s), I will be making 2005 onward my focus.
8th to War
The Eighth Doctor was the first to kiss a companion, and he revealed a much lighter, more romantic side to time travel. This was one of his most attractive qualities, but it also ended up being his greatest flaw, as he found himself unable to face the grim reality of the Time War.
In ‘The Night of the Doctor’ mini-episode we saw him come to terms with the role he must play in Gallifrey’s future. So with the use of an Elixir that allowed him full control over his regeneration, the Doctor chose to stop being a healer and start being a warrior. He became a tougher, less forgiving man, who was gradually worn down into the self-loathing character we saw in ‘The Day of the Doctor’.
This is the only time we have ever seen the Doctor choose his next body with full autonomy. One branch of this theory states that the Elixir the Doctor drank had a lasting impact on his future regenerations – but this theory could take up another article on its own.
War to 9
Even though we didn’t manage to get Christopher Eccleston back for the 50th anniversary, we still saw the War Doctor in his final days turn from an embittered, hardened warrior back into a lively, joyful man with hope for the future.
This may have been the War Doctor’s subconscious intention for his successor – a younger, more invigorated Doctor with a renewed purpose. But unfortunately the Doctor’s overlapping time streams meant he could not retain any of these positive memories. So while the regeneration still produced a young man with a refreshing energy and passion, he was also full of hatred, anger, and self-doubt.
The War Doctor did not go out in a blaze of glory, but he didn’t want that anyway. He lived his life burning bright, never resting, and sacrificing his own wellbeing for the sake of the universe. He was more than happy to die of old age – an end that many warriors are not lucky enough to have.
9 to 10
The Ninth Doctor lasted only one series, but in that short time he made his mark on Doctor Who history. A traumatised, hardened veteran of the Time War, his hostility towards the Daleks was like no other Doctor before him. Where other incarnations would quietly seethe and plot their downfall, the Ninth Doctor could not hold back his vitriol.
The presence of Rose in his short life was his therapy. She was the companion who reminded him of the beauty in the universe, and the value of mercy. In his final episode ‘The Parting of the Ways’ he was faced with a character-defining dilemma: destroy the entire Dalek and human races together, or let both live.
Any earlier in Nine’s tenure and he may have chosen the former option, but after meeting Rose his love for humanity was revived. So in his final moments it is very likely that he was thinking it was time to drop this shy, reclusive persona. He had to move on from his past, and to become the man he thought Rose deserved – a good-looking man with charm, wit, and incredibly nice hair.
10 to 11
Saying that the Tenth Doctor’s legacy to Doctor Who was monumental would be an understatement. During David Tennant’s reign, the show was more than a sci-fi show for nerds; it became mainstream viewing across the world. There’s no mystery why – he was funny, charismatic, and his quirks were unique and endearing.
But in his darker moments we saw a moody, vain man with an out-of-control god complex. As the last of the Time Lords, the rules of time were his to command. He surrounded himself with as many companions as possible, all of whom admired him and would continue to boost his ego.
In Ten’s last episode, his big turning point came when he sacrificed his life for Wilf’s, and started to accept that he was not a god – he was simply an alien traveller who had no basis to distinguish right from wrong. He finally realised that there was value in lives other than his own.
But he still wasn’t done running from his past. His old age and guilt was simmering beneath the surface, and he wasn’t ready to let go of his youthful charm yet.
11 to 12
Matt Smith’s Eleventh Doctor got even younger than his predecessor, becoming childlike in his sense of wonder and outlandish confidence. He no longer saw himself as a god – now he was nothing more than a madman in a box. He was the Doctor who couldn’t sit still, who defeated his enemies with nothing but his reputation, and who could pull off wearing a fez with aplomb. Eleven didn’t have the patience to hang around in one place for too long, because there was always more of the universe to see.
His period of depression after losing Amy and Rory brought out a darker, more stoic side to his character, and he began to mellow out a little. His impatience was still there, but it started to manifest through his intolerance for human error.
Clara put him in his place though, constantly subjecting him to her own incredibly high standards and helping him remember that not even he was faultless. Through Clara he found it in himself to overcome his impatience, and live on Trenzalore for over 1000 years simply to defend a small village from alien threats.
Eleven was also the Doctor who discovered the truth about Gallifrey: that it was never destroyed, and it was instead hiding in a pocket universe somewhere. With this knowledge, this once-hyperactive Doctor learned to accept his age, his past, and the faults of those around him. He had always been trying to hide the old man inside by presenting a youthful exterior, but now it was time to drop this façade.
During his time on Trenzalore he was reminded that each human life is sacred. So during his regeneration into Twelve he subconsciously took the face of Lobus Caecilius, an ancient Roman man whom he saved as a last-minute decision centuries ago in Pompeii. He gave himself this appearance as a reminder that even in times of self-doubt, his number one priority was to save people.
12 to 13?
So we get to our current Doctor, Peter Capaldi. Twelve started off as a grumpy, cynical old man in Series 8, then hit his wild mid-life crisis in Series 9, and this year in Series 10 we saw him settle down somewhere between the two as a university lecturer. He always struggled interacting with humans on an emotional level, failing to be of any comfort to them while they were grieving their loved ones, and at times even manipulating their deaths to his advantage.
Between the two extremes of the antisocial Series 8 Doctor and the reckless Series 9 Doctor, there was a man who was simply trying to do his best for the universe and his friends. He finally managed to capture the essence of this in his most recent episodes, as he attempted to forge a genuine heartfelt connection with Missy. He not only forgave her for misdeeds, but he even admired her a little for being able to overcome her darker temptations.
And perhaps it is this respect for Missy that will play a part in Twelve’s regeneration into Thirteen. He was his own worst enemy many times throughout his run, and it is possible that he is now taking a leaf out of his best friend’s book by subconsciously choosing to become a woman. This change of sex symbolises a completely new path for him, maybe as an attempt to shed his faults and move further away from the person he was.
Capaldi only has one episode left as the Doctor, and anything could happen in those 60 minutes that could affect this theory. There are also so few details about the personality of the Thirteenth Doctor that is difficult to speculate how this segue will take place. But what is fantastic about this theory is that it leaves open so many possibilities for future regenerations, and for as long as Doctor Who lasts we will be able to keep building upon it.