Tardis

Spoilers are precisely defined here. Rules vary by the story's medium. Info from television stories can't be added here until after the top or bottom of the hour, British time, closest to the end credits roll on BBC One. Therefore, fans in the Americas who are sensitive to spoilers should avoid Tardis on Sundays until they've seen the episode.

READ MORE

Tardis
Advertisement
Tardis
Recursion
Recursion_ploy_-_Doctor_Who_Castrovalva_-_BBC

Recursion ploy - Doctor Who Castrovalva - BBC

Recursion explained. (TV: Castrovalva)

Recursion was the concept that ideas and concepts, as Nyssa put it, "fold back on themselves". Trying to come to grips with the concept, Tegan surmised that "if we had an index file we could look it up in the index file under 'index file'".

When Mergrave assured the Fifth Doctor that he was telling the truth because "I maintain that I am, and I am a man of my word," the Doctor called it a "perfect example of recursion".

The Doctor later realised that Castrovalva itself was — as a mathematical construct of the Master — inherently recursive. The Master intended to trap the Doctor there as the recursion folded in on itself and the reality collapsed. (TV: Castrovalva)

Advertisement