Dimensional transcendentalism

A dimensionally transcendental (sometimes called transcendentally dimensional) object was one which appeared larger inside than outside, an effect made possible by transcendental engineering.

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". (DW: The Robots of Death) Rory Williams later surprised the Doctor with his understanding of the principle, that the inside was "basically another dimension." (DW: The Vampires of Venice)

The relationship between the interior and exterior sizes of a TARDIS could be controlled via the dimensional stabiliser. (DW: The Time Meddler) Known dimensionally transcendental objects other than TARDISes included Dalek time machines, the SIDRATs constructed by the War Chief, the Genesis Ark, the Doctor's pockets, and The Towers of Canonicity and Likelihood on Gallifrey. (DW: The Chase, The War Games, Doomsday, The Runaway Bride, The Vampires of Venice; EDA: The Gallifrey Chronicles)

Some of the Doctor's incarnations had a habit of pulling a wide array of items from their pockets, presumably an effect of dimensional transcendentalism. These incarnations included the Second, Fourth, Seventh, Tenth and Eleventh Doctor. It was also known that the Daleks were capable of creating dimensionally transcendent factory ships. (EDA: 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. (NA: Happy Endings)

Jack Harkness said that a PhiCorp warehouse was "bigger on the inside", although he appears to have been referring simply to the unexpectedly large number of drugs hidden there, rather than to true dimensional transcendentalism. (TW: Dead of Night)