William Shatner remembers well the day his life, and American television, changed.

“A great playwright, Norman Corwin, had written a play for me,” recounted Shatner over the phone recently, “and we were performing it in Salt Lake City, in a world premiere, on our way to New York with it. And I got the call that the pilot I had done for this show had sold, and I now had to give up the play to go do this series called ‘Star Trek.’ ”

As the show progressed, what was originally conceived as a fairly straightforward sci-fi action show started to become something more resonant.

“It was going to be running and jumping. That story about ‘Wagon Train to the Stars’ is true,” Shatner, who will appear at the Star Trek Convention Sunday, explained. “And I’m not sure how it evolved into a philosophical story. But I do know that we had access to some of the great science-fiction writers of the time, and they, in their genius, would take a science-fiction story and make it if not allegorical at least pertaining to humans of today.”

The show spawned one of the longest-running franchises in entertainment history. (The latest movie, directed by geek darling J.J. Abrams, came out in May.)

As for the notoriously devoted — and oft maligned — fan base, Shatner has a theory.

“When I shot the documentary, which is called ‘Get a Life,’ I happened upon deeper information, which is that it’s a mythology,” he said. “ And these conventions are fulfilling a mythological need that human beings are hard-wired for. Because we want an explanation of things that are mysterious, and that we have no understanding of. Thus began religion, and thus began all these various beliefs that humans have for explaining what is mystical.

“They are indulging in the ritual of mythology by coming to these conventions, by coming dressed up and getting the signature and taking the picture. It’s all participation, very much like the rituals of many of the religions.”

So, that makes Shatner a god, right?

“I would prefer the term hero,” Shatner joked. “Or demigod, how about that?”

(On the honoring heroes front, Shatner has done a documentary called “The Captains,” about the actors who succeeded him in the franchise.)

Shatner will take the stage Sunday with Kate Mulgrew, who played Captain Kathryn Janeway on “Star Trek: Voyager.” Also scheduled to appear at the convention are “Star Trek: The Next Generation” stars LeVar Burton, who played Geordi La Forge, Marina Sirtis, who played Counselor Deanna Troi, and Denise Crosby, who played Lt. Natasha Yar.

Brian Thomas Gallagher: bgallagher@seattletimes.com