Temporal grace was the term used to describe the state in which the interior of TARDISes existed. Supposedly, it ensured no weapons could be used inside the Doctor's TARDIS. (TV: The Hand of Fear, The Invasion of Time) It was linked to the TARDIS' telepathic circuits, and when fully functional, it would negate all hostile and aggressive actions within the ship. (PROSE: The Bodysnatchers)
Uses of temporal grace Edit
When nuclear missiles were launched on an alternate Earth, the Doctor materialised the TARDIS around the whole planet so that the temporal grace would prevent the missiles from exploding. (PROSE: Blood Heat)
Temporal grace prevented guns from being used against Nobody No-One, but since he was from another dimension (and as such, operated under different laws of physics), this did not apply to him. (AUDIO: The Word Lord)
The Eighth Doctor repaired the state of grace circuitry. When he drew several Skarasen into the TARDIS, he told his companions that the state of grace within the ship meant that the creatures couldn't harm them. (PROSE: The Bodysnatchers)
Failures of temporal grace Edit
Nyssa asked the Fifth Doctor about temporal grace not stopping the Cybermen from firing weapons inside the TARDIS, but he only replied, "Nobody's perfect." (TV: Arc of Infinity) Ace also questioned the Doctor about temporal grace after the interior nearly disintegrated. (PROSE: Blood Heat).
Sontarans (TV: The Invasion of Time), Cybermen (TV: Earthshock, Attack of the Cybermen), a Terileptil android (TV: The Visitation) and a Dalek (TV: The Parting of the Ways) discharged their guns in the TARDIS.