The IDIC symbol became an integral part of Vulcan history.
The IDIC (Infinite Diversity in Infinte Combinations) symbol was introduced to Star Trek: The Original Series by Gene Roddenberry who was selling medallions with the symbol through his company, Lincoln Enterprises. The script for “Is There No Truth In Beauty?” contained quite a bit of information about the medallion, and after Leonard Nimoy protested, Roddenberry explained that it was meant as a product placement to help generate sales. Eventually, the scene was whittled down in the episode and barely even registered with the audience.
The third season episode of The Original Series was the introduction of the Vulcan symbol to the Trek universe, but originally, it was going to be introduced in the first episode of the third season, “Spock’s Brain,” and it had quite a larger role.
Gene Roddenberry wanted to include the IDIC medallion in an epilogue of “Spock’s Brain.”
In a 1969 memo to Freddie Freiberger who was the producer of the third season of TOS, Roddenberry wrote an epilogue to “Spock’s Brain” that had Lt. Uhura and some junior officers presenting a gift to Spock as a gesture of gratefulness that he was alive. The memo, as shown by The Trek Files, suggests that the gift of the IDIC medallion came about because Chekov had done research, looking for what to give a Vulcan.
Roddenberry’s suggestion had Spock launching into a long description of the story behind the symbol and what it means to Vulcans. In fact, Spock was supposed to become so animated he was “chattering away like a human.” Captain Kirk, Dr. McCoy, and Scotty would have attempted to interrupt Spock with ship’s business, but he wouldn’t stop talking which would have led Dr. McCoy to say the line about how he wished he hadn’t reconnected Spock’s mouth.
Thankfully, this scene didn’t come to pass as it would have taken Spock totally out of character and, with such importance to him, one would question why the medallion or symbol hadn’t been shown sooner.
How the medallion moved from “Spock’s Brain” to “Is There No Truth in Beauty?” is a mystery. But the IDIC symbol has continued as a part of Vulcan philosophy, making appearances in The Next Generation, Voyager, Deep Space Nine, Enterprise, Discovery, and Picard, as well as four Star Trek movies.