“So the thing you have to understand is this is radio,” says the voice in the darkness — a little bit squeaky, a little bit nasal, not at all the voice you’d assign to the leader of a benign radio cult if it weren’t already so familiar.

Ira Glass, creator and host of the weekly public radio story anthology This American Life, begins all his speaking engagements this way. That opening line is always good for a laugh. But at GW Lisner Auditorium Saturday night, Glass kept his audience in the dark for the first few moments while he riffed on the sense of intimacy that makes radio such a powerful storytelling medium. It was a memorable beginning to an inspiring two-hour discussion of the techniques of storytelling as practiced by the staff of This American Life, and the reasons stories are so indispensable to our humanity.