Doctor Who Series 12: Ten Huge Questions After Praxeus
5. How Many Brains Does The Doctor Have?
We know that the Doctor as a Gallifreyan Time Lord has two-hearts. It was a fact established in Jon Pertwee’s debut story Spearhead from Space when suffering from amnesia he is x-rayed in hospital. A similar scene takes place in the 1996 TV Movie. Initially dismissed as a double exposure, the surgeon Grace is forced to accept the x-ray is a true picture of the Doctor’s alien anatomy. More recently, in The Power of Three (2011) Kate Stewart takes a scan of the Doctor’s hearts.
But what of the Doctor’s brain or brains? In the Tom Baker story, The Invisible Enemy, the Doctor and Leela make minituare clones of themselves and journey inside the Doctor’s mind, literally, in order to destroy the Nucleus virus. Those who played the 1990s computer game, Destiny of the Doctors will also remember a boss battle inside the Doctor’s brain. The assumption was always of a single brain, though one far superior to that of a human.
The closest we get to the idea that the Doctor might have more than one brain is in Extremis (2017), where Missy is said to have two hearts and three brain stems. If they are both marks of a Time Lord then the Doctor might also have three brains.