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 as it gave them power over others, they accused the Doctor of witchcraft when he gre another hand. (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)

Notes

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.