William Jackson Harper is nervous. He and I have been on the phone for five minutes, and he’s walking around his living room as we speak, analyzing everything he’s saying and hoping he hasn’t said anything stupid. I can relate.

“Are you pacing right now?” I asked. “Because I pace all the time.”

“Yeah, I’m pacing,” he said. “I am.”

As a self-described neurotic, he takes his nervousness as a given. Later, he tells me about how hard it is to make dinner plans. He and his girlfriend have talked about it. How there’s something about making the plans in advance that fills him with dread. As he shares all this and more, I can tell he’s smart. Funny. A little awkward. These qualities and idiosyncrasies are just some of what he brings to one of the best roles on television. They’re also qualities people probably see when they say to me, “You’re such a Chidi.”

Harper , 39, plays the eternally indecisive professor Chidi Anagonye on NBC’s “The Good Place.” The fervently celebrated sitcom, which begins its fourth and final season on Thursday , makes a heady, candy-chili stew out of deeply surreal comedy and profound, often heartbreaking explorations of morality. Chidi, more than his fellow humans and the extra-dimensional beings in their orbit, is the philosophical heart of the show.