Clarke's Law

Clarke's Law states that:


 * Any sufficiently advanced form of technology is indistinguishable from magic.

To use but one example, the Sycorax thought of blood control as form of sorcery and the Doctor as a user of witchcraft. (DW: The Christmas Invasion)

The 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. (DW: Battlefield).

The Captain paraphrased this by describing now-wrecked craft had possessed technologies "indistinguishable from magic" (DW: The Pirate Planet).

Note
This principle often gets quoted as a singular statement. In fact, Arthur C. Clarke made it the third of three laws concerning predicting the future.