Philosophy of Star Trek:
"Intolerance in the 23rd century? Improbable!
If humankind survives that long, we will have learned to take a delight in the essential
differences between people and between cultures. We will learn that differences
in ideas and attitudes are a delight, part of life's exciting variety, not something to fear.
It's a manifestation of the greatness that God, or whatever it is, gave us. This infinite
variation and delight, this is part of the optimism that we built into Star Trek."
— Gene Roddenberry
The triangle and the circle are two different shapes, materials, and textures. They represent any two diverse things which come together to create truth or beauty, represented by the jewel in the center.
IDIC (from the Star Trek Concordance, 1976):
The most revered Vulcan symbol, combining variations in texture, shape, and color. The name is Terran, an acronym for "Infinite Diversity in Infinite Combinations"; the Vulcan name is not known. (This has changed since 1976, see below)
Spock's IDIC, which can be worn as a pin or as a pendant, is a circle and triangle of white and yellow-gold metals in shiny and textured (or Florentine) finish, with a white jewel. Spock explains that the different shapes and materials represent the diverse things which come together to create truth and beauty; the glory of creation lies in its infinite diversity and meanings. ("Is There in Truth No Beauty?")
Kirk recalls to the Spock-clone the philosophy of the Vulcan IDIC and what it means. He also asks if an army of Spocks could impose peace on the galaxy and make other beings accept the Phylosian philisophy in defiance of the Vulcan IDIC concept. The Spock-clone decides that it cannot be done. ("The Infinite Vulcan")
The above text is taken from The Star Trek Concordance by Bjo Trimble, 1976
From the vulcan-l Vulcan FAQ:
Steve Boozer has this additional item:
According to the unnamed Vulcan Master who tutored teenaged Tuvok, it is called kol-ut-shan - "the cornerstone of our beliefs" [VOY "Gravity"].
In fandom the IDIC is also called t'triahve.
In Traditional Golic Vulcan the term used is Va'Vuhnaya s'Va'Terishlar. Another term for the concept is Kol-uchang.
"Is There in Truth, No Beauty?"
The IDIC medallion first appeared in the third season of the original series in the episode "Is There in Truth, No Beauty?" with an explanation of it's symbolism given in the dinner scene. The complete version of that explanation was not in the aired version of the episode, but was in the final, unfilmed draft. Following are both versions—research and italicized comments by Greg Schnitzer.*
— Gene Roddenberry
The wisdom of