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)