- Doctor Who: "The cheeseboard is the world, and the pieces the phenomena of the universe," as my old friend Huxley used to say... Cheeseboard? Chessboard. "And the opponent makes no allowances for mistakes nor makes the smallest concession to ignorance." I'm an ignorant old Doctor, and I've made a mistake.
- The Monitor: For many uses, machinery is unsurpassed, but Logopolis is not interested in such uses. Block Transfer Computations can not be done with computers.
- Adric: Why not?
- The Monitor: Our manipulation of numbers directly changes the physical world. There is no other mathematics like ours.
- Adric: D'you mean the computations themselves would affect a computer?
- The Monitor: Of course. Change it's nature; cause it to malfunction. Only the living brain is immune.
- The Master: Logopolis is a cold place... a cold high place overlooking the universe. It holds a single great secret, Nyssa, which you and I must discover together.
- The Master: Logopolis is not the universe.
- The Monitor: But it is. Logopolis is the keystone. If you destroy Logopolis, you unravel the whole causal nexus.
- The Master: "Causal nexus" - you insult my intelligence.
- The Master: If we do cooperate, there'll be no question of you ever returning to Gallifrey.
- Doctor Who: If we don't cooperate, there'll be no question of Gallifrey.