Clarke's Law
Clarke's Law stated that:
Any sufficiently advanced form of technology is indistinguishable from magic.
The Seventh Doctor reminded Ace of Clarke's Law and stated that "the reverse is true", as was the case of the Thirteen Worlds, a parallel universe where technology formed alongside magic. (TV: Battlefield)
The Captain paraphrased this by describing now-wrecked craft had possessed technologies "indistinguishable from magic." (TV: The Pirate Planet)
Although not referenced specifically, the Sycorax proved Clarke's Law, by thinking of blood control as form of sorcery, due to it giving them power over others. (TV: The Christmas Invasion)
When Angelo Colasanto believed Captain Jack Harkness' Vortex manipulator to be magic, Jack corrected him saying it was technology, although the two could be indistinguishable. (TV: Immortal Sins)
Behind the scenes
In the real world, this is actually Arthur C. Clarke's Third Law.
