Temporal grace

Temporal grace was a term used to describe the state in which the interior of the TARDIS existed. Supposedly, it ensured that no weapons could be used inside its environs. (DW: The Hand of Fear, The Invasion of Time) However, on other occasions, it seemed that no such defense existed. Cybermen (DW: Earthshock, Attack of the Cybermen) and a Dalek, for example, have discharged their guns in the TARDIS. (DW: The Parting of the Ways)


 * It is possible that the Doctor is able to disable temporal grace, or that it is merely a bluff to convince people not to attempt violence in the first place.