Vulcan IDIC Seal

Cthia was a Vulcan word, typically translated into English as "logic", but actually possessing the more complex meaning of "reality-truth". The term cthia was also often used to refer to the philosophy/religion of logic, emotional control, and pacifism preached by Surak. (TOS novel: Spock's World)

Cthia was harder to sustain for those who were not wholly Vulcan. (TOS novelization: Star Trek)

Tuvok taught his children the fundamental principles of Vulcan cthia. (TTN novel: The Red King)

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