A Vulcan thinker whose first law of metaphysics, that nothing unreal exists, is among the questions put to Spock by the testing computers during his re-education after the fal-tor-pan.
Kiri-kin-tha was a Vulcan philosopher, known for at least one numbered law of metaphysics. The first law states simply that nothing unreal exists, a maxim typical of Vulcan thought in turning a statement about reality into a discipline for the mind.
The name is heard in Star Trek IV: The Voyage Home. Three months after his body and katra were rejoined, Spock stands among several computer stations on Vulcan answering rapid questions on chemistry, mathematics, chess and philosophy to retrain his memory. One asks him for Kiri-kin-tha's first law and he supplies it without hesitation, moments before the machine defeats him with a question his human mother has to explain: how do you feel?
Nothing else is established about the philosopher, who is never seen.