The latest era of Doctor Who has had a controversial start, kicking off with one of the most surprising new elements in the show’s history, bi-generation, but that could lead to a perfect send off for Ncuti Gatwa’s Doctor. Russell T Davies was the man who originally brought Doctor Who back in 2005, and now, almost two decades later, he’s done it again. However, this time has been a mixed bag when it comes to reviews for the reboot. From controversial new stories, to disappointing finales, RTD2 is an odd mix of fantasy and callbacks that feel a bit jarring.

Despite this, there is one element that was introduced which could actually lead to an incredible full circle finale for the latest Doctor, played by Ncuti Gatwa. During the 60th anniversary specials, the Doctor regenerated after being attacked by the Celestial Toymaker. But, this time was different to anything that came before, and the Doctor experienced something completely new called bi-generation. While the event split fans just as it did the Doctor, it could be the perfect set up for an epic final encounter between the Fourteenth Doctor, played by David Tennant, and the Fifteenth Doctor, played by Ncuti Gatwa.

Doctor Who Season 14 Confirms The Doctor’s Soul Has Been Split In Half

The Doctor Is Not Who He Used To Be

While bi-generation came across as a novel concept, Doctor Who season 14 did go part of the way to explaining the process behind the monumental new change. While on the outside, it looks plain and simple that the Doctor split into two distinct beings, both with independent lives, it’s likely that the split had more lasting consequences. The Doctor may be an alien, and capable of some incredible tricks, but splitting like an amoeba seems like it might just be a touch too far.

And Gatwa’s Doctor confirms this in episode 2, “The Devil’s Chord,” when he says to his companion, Ruby Sunday, played by Millie Gibson, “it tore my soul in half.” This could be a sign that what happened with the regeneration was not sustainable, and it may have to be reversed at some point in the future. As much as splitting in two to deal with traumas and give the Fourteenth Doctor a shot at normal life may be nice, it certainly doesn’t seem like that could be permanent. A half soul doesn’t sound too pleasant, and ultimately would indicate that this version of the Doctor needs to be made whole.

The Current Doctor Being “Halved” Sets Up Becoming Whole Again In The Future

Two Halves Together Make A Whole

In Doctor Who’s 60-year history, the Doctor has yet to experience being halved, despite there being numerous times when there is more than one Doctor. The multi-doctor adventures saw the Doctor come face to face with other incarnations of himself from different periods in his life. Tennant’s Tenth Doctor lost a hand that eventually absorbed some regeneration energy to grow into a new body. And Donna had part of the Doctor’s mind imprinted on her own, resulting in the Doctor Donna. However, in all of these situations, the Doctor remained a whole individual.

On the occasion of the Fourteenth Doctor’s regeneration, the split meant that the singular Doctor became two fractured parts of himself, stuck in the past, and one running toward the future. But, by necessity, it would make the most sense for this Doctor to need to be whole once more before he can regenerate. Otherwise, the Doctor remains fragmented and divided in his body, with part of his actual body and mind living outside of his current state.

Theory: The Doctor Must Become Whole Again In Order To Regenerate

Tennant & Gatwa Reuniting

So, if the above is true, and the Doctor is a half soul, with the need to be reunited with his other half, it could be a major hint about how RTD will resolve the bi-generation story. The Doctor, living with only part of his body, must reunite the parts of his being in order to properly activate his Time Lord powers of regeneration. While it is likely that Ncuti Gatwa has more time ahead of him to play the Doctor, there is always a handover that comes for any actor who tackles the role.

It is unlikely that Gatwa will remain in the role for so many years that RTD couldn’t plan ahead for his regeneration. And if RTD did come up with a reason for fan favorite Doctor actor, David Tennant, to return as a new incarnation, it is possible that he planned ahead to a future date where he could bring that story back around. Potentially, the Fifteenth Doctor would be unable to even regenerate without his whole self, and it would force Gatwa and Tennant’s Doctor’s to meet again ahead of his final moments before regenerating into a whole Sixteenth Doctor.

Tennant & Gatwa’s Doctors Rejoining Would Work As A Doctor Who Story

It Makes For A Great Doctor Who Regeneration Story

Both RTD and Steven Moffat have included lengthy overarching stories during their tenures as showrunners, which helped to mark their time on the show, and add to their Doctor’s stories. It is plausible that RTD thought ahead to the moment when Gatwa’s Doctor would regenerate and imagined another moment to bring Tennant back briefly. This is not necessarily to overshadow Gatwa’s Doctor, but it would provide a satisfying story with a full circle ending. It would also create a perfect endpoint for both Fourteen and Fifteen, after the two have done all that they needed and wanted to do.

Fifteen made it clear that the bi-generation happened in order to give the Doctor adequate time to work through his previous problems, and still be able to run through the stars uninhibited. But if that is what happens, surely the two must reunite at the end to complete the cycle of healing. And for Fourteen, having spent time with Donna and her daughter, he remains a being with an extremely long life. Eventually, they will pass away, and Fourteen would remain alone, unless Doctor Who sees the two come back together, and finally closes the book on the Doctor’s bi-generation storyline in a way that feels deliberate and well-thought-out.