Symbolic logic

Symbolic Logic was the basis of the Cybermen's control systems present in the Telos Cyber-tombs in order to test and provide humans that who great inelligence, to be subjected to Cyber-conversion and become the new race of Cybermen. The controls must have required a genius to solve them as Eric Klieg, a member of the Brotherhood of Logicians was unable to work the controls unaided by the Doctor. The controls themselves consisted of a series of buttons and levers which had to be pushed and pulled in the correct sequence to operate the Cyber-Technology present within the Tombs. (DW: The Tomb of the Cybermen)


 * It remains unclear whether the Cybermen used symbolic logic purely for testing the intelligence of their "candidates" or if they used for all their control systems.