My theory as to what the Tardis is

[Atrahasis]

The Tardis has inside it the Eye of Harmony which is a power that could have destroyed the Earth and apparently the universe had the Doctor not closed it as he did in the TV movie. The Eye also brought Grace and Lee back to life.

Inside the Tardis console in the Eccleston/Tennat era is an energy source that knows all of space and time and can destroy and create anything, and even turned Rose into an omnipotent and omniscient being for a short time.

The Tardis is also characterized to be sentient.

Now consider the Universe...is it sentient? Sometimes I get the feeling that it's the Universe itself that is operating at the heart of the Tardis, and this universe is a sentient one.

Short of calling it "God", there seems to be very little that this power at the heart of the Tardis cannot do.

But if we define omniscience and omnipotence and eternity with God, then we would have to call the Tardis' heart exactly that.

The Tardis is God-powered!

Imagine the technology involved that can access God himself. Those clever Time Lords!

[CaptainPierce]

Hmm, if the Tardis is God-powered, the Christian Conservatives might finally start paying attention to the minimum wage and other labor laws...

[MajorRacal]

The nature of the TARDIS has evolved and grown highly confused and contradictory over the years. From the start it was simply a machine, and more commonly referred to as 'the ship' by the Doctor. The element of sentience was alluded to more from the Pertwee era but this was never fully explored or explained and many authors have interpreted this to suit their own views. The Eye of Harmony was not originally an element of any TARDIS and was a device used to control an artificial black hole created by the Timelords (the black hole is credited to Omega in The Three Doctors; the Eye of Harmony is first mentioned in The Deadly Assassin some years later, along with other ancient artifacts left behind by Rassilon). The presence of the Eye of Harmony within the Cloister Room of the TARDIS only came about in the TV movie, which in many ways contradicts elements of the original 26 year run. The new series further blends and contradicts all of this. All TARDIS's were somehow connected to a massive database which spanned all time and space and was known as The Matrix - this was situated on Gallifrey itself. The all powerful godlike nature of the TARDIS is a fresh departure with little correlation to the original 26 year run. Doctor Who is not a series that has ever prided itself on continuity, and despite many fan attempts to rationalise technology, timelines and contradictions, no-one has succeeded in resolving all the inconsistencies.