Dimensional transcendentalism



Dimensional transcendentalism was the state wherein an object's interior was bigger than its exterior, an effect made possible by transdimensional engineering.

History
The Fourth Doctor once explained the principle to Leela by using the analogy of how a larger cube might appear to be able to fit inside a smaller one were the larger cube further away, yet immediately accessible at the same time. He described this as "a key Time Lord discovery". (TV: The Robots of Death) Rory Williams later surprised the Eleventh Doctor with his understanding of the principle, that the inside was "another dimension". (TV: The Vampires of Venice)

The relationship between the interior and exterior sizes of a TARDIS could be controlled via the dimensional stabiliser. (TV: The Time Meddler) Dimensionally transcendental objects other than TARDISes included Dalek time machines, (TV: The Chase) the SIDRATs constructed by the War Chief, (TV: The War Games) the Genesis Ark, (TV: Doomsday) the Doctor's pockets, (TV: The Runaway Bride, The Vampires of Venice), the Towers of Canonicity and Likelihood on Gallifrey, (PROSE: The Gallifrey Chronicles) and clown cars from the planet Semtis. (PROSE: Shroud of Sorrow)

Sometimes when a TARDIS was dying, its dimension dams would start to break down in what was called a "size leak". The Eleventh Doctor described it as "All the bigger on the inside starts leaking to the outside. It grows." This happened to the Doctor's TARDIS, as it was dying on Trenzalore. Here it served as the Doctor's tomb in an alternative timeline in which the Time Lords never granted the Doctor a new cycle of regenerations at the conclusion of the Siege of Trenzalore. Prior to his battle, the Eleventh Doctor and Clara Oswald discovered the ruined TARDIS relative to his future when they went to Trenzalore. It still appeared as a police box but was much larger. Clara described it as "one hell of a monument." (TV: The Name of the Doctor)

The Daleks were capable of creating dimensionally transcendent factory ships. (PROSE: War of the Daleks)

The Doctor temporarily expanded the interior dimensions of a boarding house in Cheldon Bonniface to allow all the guests at Benny's wedding to stay there. (PROSE: Happy Endings)

Upon meeting the Teselecta, "a robot worked by tiny people", the Eleventh Doctor, wondering how they could all fit inside, briefly suggested that it was bigger on the inside until he discovered it was via basic miniaturisation sustained by a compression field. (TV: Let's Kill Hitler)

began working on St Paul's Cathedral to make it bigger inside in an attempt to create and army of Cybermen out of the dead which she stored in tombs filled with dark water. (TV: Dark Water, Death in Heaven)

It's bigger on the inside
Many of the Doctor's companions were in awe of police box that was larger within, often commenting that "it's bigger on the inside." (TV: The Three Doctors, Robot, Rose, The Runaway Bride, Smith and Jones, The Eleventh Hour, The Bells of Saint John) The Doctor looked forward to this. (TV: The Vampires of Venice) However, one version Clara surprised the Doctor by saying the reversed phrase, "It's smaller on the outside." (TV: The Snowmen)